OPINION OF THE COURT
GREENBERG, Circuit Judge.
American Telephone and Telegraph Company appeals, invoking jurisdiction under the collateral order doctrine, from orders of the United States District Court for the Eastern District of Pennsylvania of July 27, 1990, and November 7, 1990, in this action involving claims brought against it by the Communication Workers of America (CWA) involving two of the Union’s units. The complaint alleged that AT & T had contracted work out to nonbargaining unit employees in violation of its agreement not to do so. AT & T moved for a summary judgment, claiming that the contracting out grievances were not justiciable under the collective bargaining agreement and that determinations in grievance processes concerning the disputes were final.1
The district court denied summary judgment by order of July 27,1990, as to claims arising from the Business Units division, as it found that they were justiciable. It nevertheless dismissed the complaint insofar as it advanced those claims as they had not been properly pleaded. The dismissal, however, was with leave to amend so that they could be correctly asserted. The district court did not rule on the substantive issue raised by AT & T’s motion, i.e. that thé grievance determinations were final, as to the other unit involved, the Material Management Service unit (MMS), since it found that the MMS claims were subject to an arbitration exhaustion requirement. It thus dismissed the complaint in its entirety. AT & T then moved for reconsideration but [202]*202the district court denied this motion by order of November 7, 1990.
In addition to appealing, AT & T has filed a petition for a writ of mandamus under 28 U.S.C. § 1651 asking us to direct the district court to enter judgment in its favor with respect to the Business Units claims. Furthermore, it asks us to direct the district court to vacate its order of arbitrability regarding the MMS claims and to rule on its motion for summary judgment as to those claims. We will dismiss the appeal and deny the petition for mandamus.
I. BACKGROUND
The Agreements Between AT & T and the Union
AT & T and the CWA are parties to a National Operations Memorandum of Understanding effective May 28, 1989, through May 30, 1992, applicable to distinct CWA bargaining units by means of separate collective bargaining agreements. The bargaining units involved here, the Business Units and the MMS units, are parties to collective bargaining agreements implementing the Memorandum of Understanding.
The Memorandum of Understanding contains a letter, the Bahr-Williams letter, from Raymond E. Williams, AT & T’s Corporate Vice-President of Labor Relations, to Morton Bahr, General President of the International Union, addressing contracting out providing:
Dear Mr. Bahr:
I am writing to respond to the expressions of concern raised at the Operations bargaining table regarding the Company’s contracting out of work, which have focused on situations in which a layoff is pending or has occurred (and ex-bargaining unit members retain recall rights) within the same geographical commuting area where the work is to be contracted, and in job titles whose occupants would traditionally have performed such work. I do not believe that CWA and AT & T have diverse views on this subject.
As to other work normally performed by our employees, we have always preferred not to contract such work out if it would otherwise be performed by bargaining unit employees in job titles in a geographical commuting area (1) where layoffs of such employees are pending; or (2) where a layoff has already occurred and such laid off bargaining unit members retain recall rights and are available to perform such work.
In the future, the Company will not contract out such work, under the conditions outlined above, except when it has no other reasonable alternative. Under such circumstances, the Company will discuss the decision with the Union.
Very truly yours,
RAYMOND E. WILLIAMS
The Bahr-Williams letter also appears in the agreement booklets containing the individual collective bargaining agreements. However, the Memorandum of Understanding provided that the Bahr-Williams letter was not part of the agreement(s):
The following matters [including the Bahr-Williams letter], which have been the subject of negotiations between the parties, are settled and disposed of, and are set forth in this Part II in as much as they are not included in the 1989 Agreement, and although one or more provisions, attachments, or letters may be reprinted in the 1989 Agreement, these matters are not to be considered a part of the 1989 Agreement.
In addition to reprinting the Bahr-Williams letter, the individual agreements addressed other matters relevant to our determination of this case. Article 9 of the Business Units agreement provided:
The Company and the Union recognize and confirm that the grievance procedures set forth in Article 9, and, where applicable, Article 10 (Arbitration) and Article 11 (Mediation), provide the mutually agreed upon and exclusive forums for the resolution and settlement of employee disputes during the term of this Agreement.... Neither the Company, [203]*203nor the Union ... will attempt by means other than the grievance, arbitration, and/or mediation procedures to bring about the resolution of any issue which is properly subject for disposition through such procedures.
[Emphasis added].
Article 30 of the Business Units agreement, which placed some limitation on AT & T’s right to contract out work, explicitly excluded contracting out grievances from arbitration as it provided that “[t]he provisions of this article will be subject to the grievance procedure contained in Article 9, but shall not be subject to the arbitration provisions contained in Article 10.” [Emphasis added].
Unlike the Business Units agreement, the MMS agreement did not explicitly address contracting out but Article 18 of the MMS agreement addressed “Movement of Personnel” and provided, in relevant part:
3.1 When lack of work necessitates decreasing the work force, the employees shall be selected as surplus in the inverse order of TERM OF EMPLOYMENT from the classification or occupation affected ...
Article 18 also set forth the order in which job vacancies were to be filled, calling for them to be filled by “new hires” only if an employee could not be found for the vacancy. Article 10 of the MMS agreement provided, without exclusion of disputes under Article 18, for arbitration of disputes over interpretation of provisions included in the agreement or performance of obligations under the agreement if such disputes could not be solved through the grievance procedure.
Procedural History
On January 29, 1990, CWA and two of its districts brought this action against AT & T under Section 301 of the Labor Management Relations Act, 29 U.S.C. § 185(a),2 for injunctive and other relief with respect to subcontracting practices by AT & T. CWA alleged that AT & T breached the agreement contained in the Bahr-Williams letter in which it agreed not to contract out work normally done by bargaining unit employees in areas where layoffs were pending or had taken place. CWA alleged that it had filed grievances regarding these violations which AT & T denied.3 The complaint stated that the grievance procedure was the “exclusive forum for the resolution of the disputes between the parties,” and that “[t]he parties agree that a violation of the Bahr-Williams letter agreement [was] not subject to arbitration under any of the parties’ collective bargaining agreements.” In its answer AT & T admitted the existence of the Bahr-Williams letter and the collective bargaining agreements and agreed that allegations of violations of the letter were not subject to arbitration but otherwise denied the allegations of the complaint.
AT & T then filed its motion for summary judgment, asserting that the contracting out disputes were not subject to arbitration, and the grievance procedure was the exclusive forum for resolution of the disputes. AT & T therefore urged that CWA could not obtain an. adjudication on the merits of its grievances in the district court. In short, AT & T contended that the grievance procedure was the final and exclusive method for resolving disputes over contracting out and that the Union had no recourse beyond the grievance procedure.
[204]*204By opinion and order of July 27, 1990, the district court denied the motion with respect to the Business Units grievances, holding that it had jurisdiction to hear and decide them on the merits. The court found, however, that CWA should have asserted the Business Units grievances under the collective bargaining agreement, rather than the Bahr-Williams letter. The court then determined that the Business Units agreement expressly excluded contracting out disputes from arbitration, but it concluded that since the Business Units agreement did not explicitly deny the Union the right to a judicial determination regarding its grievances, it had such a right. Thus, the court dismissed the complaint with respect to the Business Units grievances with leave to amend so that the CWA could assert a claim based upon the collective bargaining agreement.4
The district court determined that CWA’s claim regarding the MMS grievances implicated the entire collective bargaining agreement, not just the Bahr-Williams letter, and in particular noted that Article 18 of the agreement could be read to limit AT & T’s right to contract work out. The court explained that the restriction in the article of “AT & T’s right to lay off employees to situations where ‘lack of work necessitates decreasing the work force,’ ” could be read to mean that “AT & T’s continuance of the layoff may be unjustified in the event that the laid off workers are qualified to perform the subcontracted work.” Further, the court noted that “[i]t may be that AT & T, by [contracting out] the work at issue, has filled a ‘job vacancy’ with ‘new hires’ in violation of the hierarchy established by Paragraph 2 [of Article 18 for filling job vacancies].” The court found that the MMS grievances were arbi-trable since disputes under Article 18 were subject to arbitration. The court concluded that CWA could not bring suit on its contracting out claims under the MMS agreement until it had exhausted the arbitration procedures. Accordingly, it dismissed the Union’s complaint on the MMS grievances, subject to this exhaustion requirement and, therefore, never ruled on AT & T’s summary judgment motion regarding the MMS grievances.5
AT & T filed a timely motion for reconsideration of the district court’s July 27, 1990, order, urging that judgment should be entered in its favor. In the alternative, it sought entry of final judgment under Fed.R.Civ.P. 54(b) with respect to the MMS grievances and certification for interlocutory appeal under 28 U.S.C. § 1291(b) with respect to the Business Units grievances. The district court denied this motion in a memorandum opinion and order of November 7, 1990.
AT & T filed its notice of appeal on December 7, 1990, and on December 12, 1990, it filed the petition for mandamus seeking an order from this court directing the district court to enter judgment in its favor on the allegations concerning the Business Units agreements. AT & T further asked us to order the district court to vacate its order of arbitrability and decide its summary judgment motion concerning the MMS agreements. CWA then filed a motion to dismiss AT & T’s appeal for want of jurisdiction. On December 18, 1990, we ordered the appeal (No. 90-1950) and the petition for mandamus (No. 90-1936) consolidated and we now address both the appealability of the district court’s order and AT & T’s petition for mandamus.
II. APPEALABILITY
This court exercises appellate jurisdiction under 28 U.S.C. § 1291 only over [205]*205final orders of the district court. Usually a decision is final within section 1291 when it “ends the litigation on the merits and leaves nothing for the court to do but execute the judgment.” Van Cauwenberghe v. Biard, 486 U.S. 517, 521, 108 S.Ct. 1945, 1949, 100 L.Ed.2d 517 (1988) (quoting Catlin v. United States, 324 U.S. 229, 233, 65 S.Ct. 631, 633, 89 L.Ed. 911 (1945)). Here, the district court’s order would ordinarily not be regarded as “final” under 28 U.S.C. § 1291 for the court dismissed CWA’s complaint as to the Business Units grievances with leave to amend. See Newark Branch, N.A.A.C.P. v. Harrison, N.J., 907 F.2d 1408, 1416-17 (3d Cir.1990). Thus, the order rather than ending the case “ensure[d] that litigation will continue in the District Court.” Gulfstream Aerospace Corp. v. Mayacamas Corp., 485 U.S. 271, 275, 108 5.Ct. 1133, 1136, 99 L.Ed.2d 296 (1988).
AT & T nevertheless asserts that this court can exercise jurisdiction over its appeal by regarding the orders of July 27, 1990, and November 7,1990, as final pursuant to the collateral order doctrine explicated in Cohen v. Beneficial Industrial Loan Corp., 337 U.S. 541, 69 S.Ct. 1221, 93 L.Ed. 1528 (1949). Cohen held that an order of a district court entered before what would ordinarily be the final order can be reviewed if it falls within
that small class [of prejudgment orders] which finally determine claims of right separable from, and collateral to, rights asserted in the action, too important to be denied review and too independent of the cause itself to require that appellate consideration be deferred until the whole case is adjudicated.
Id. at 546, 69 S.Ct. at 1225-26.
Cohen’s progeny have established three requirements for an order to be collaterally appealable; the order must (1) “conclusively determine the disputed question,” (2) “resolve an important issue completely separate from the merits of the action” and (3) “be effectively unreviewable on appeal from a final judgment.” Coopers & Lybrand v. Livesay, 437 U.S. 463, 468, 98 S.Ct. 2454, 2458, 57 L.Ed.2d 351 (1978). The collateral order doctrine is narrow and each of the three independent requirements must be met before appellate review is permitted so as to further the important goal of avoiding piecemeal appeals. Eavenson, Auchmuty & Greenwald v. Holtzman, 775 F.2d 535, 537 (3d Cir.1985). We conclude that the district court’s orders do not meet the third prong of the collateral order doctrine since the orders will not be effectively unreviewable on appeal from a judgment at the conclusion of the case in the district court.6
Business Units
AT & T claims that the district court’s orders that the Business Units grievances are justiciable will be effectively unreviewable on later appeal because AT & T’s right to be free from litigating the contracting out issue in the district court will be irretrievably lost by the time such an appeal is taken. According to AT & T, Article 9 of the Business Units agreement provides it with immunity from having to litigate the contracting out issue in court. Thus, forcing it to litigate this issue without allowing an immediate appeal would negate the immunity bargained for by AT & T and obtained in the Business Units agreement.
In support of its argument, AT & T relies on Mitchell v. Forsyth, 472 U.S. 511, 105 S.Ct. 2806, 86 L.Ed.2d 411 (1985). In Mitchell, the district court denied a motion to dismiss by the former Attorney General who contended, in relevant part, that he had qualified immunity from an action arising out of allegedly unlawful wiretaps placed by the Justice Department on the phones of anti-Vietnam War activists. This court on appeal held that the denial of qualified immunity was not appealable under the collateral order doctrine, and that [206]*206Mitchell should wait final judgment to appeal. The Supreme Court reversed, holding that the qualified immunity which Mitchell asserted was an “immunity from suit rather than a mere defense to liability; and like an absolute immunity, it is effectively lost if a case is erroneously permitted to go to trial.” Id. at 526, 105 S.Ct. at 2815. (Emphasis in original).
We do not find AT & T’s claimed immunity equivalent to that asserted in Mitchell v. Forsyth. The immunity implicated in Mitchell was judicially created in recognition of public policy and the common law and was intended to serve the public interest in seeing that government officials carry out their duties with independence and without fear of the consequences. Furthermore, in other cases in which the right to a collateral order appeal is advanced the appellant may point to rights created in the Constitution as supporting the appeal. Thus, this court stated in Sperling v. Hoffman-LaRoche, Inc., 862 F.2d 439, 442-43 (3d Cir.1988), aff'd, 493 U.S. 165, 110 S.Ct. 482, 107 L.Ed.2d 480 (1989), that “[t]he rights protected by the Double Jeopardy clause, ... the Speech or Debate clause, ... and absolute or qualified immunity ... are sui generis for purposes of the collateral order doctrine. They protect the defendants from the trial itself.” These are important, constitutional rights, of the type contemplated by Cohen as “too important to be denied review.”
In reality, AT & T merely seeks to be free from the cost of litigating the claims. While that interest is significant, inasmuch as its foundation is contractual it is not on the qualitative level of a right to be free from trial on the basis of the protections in the Double Jeopardy or Speech and Debate clauses or on the basis of immunity recognized in judicial decisions. See Sperling, 862 F.2d at 442. Indeed, the Supreme Court “has declined to find the costs associated with unnecessary litigation to be enough to warrant allowing the immediate appeal of a pretrial order.” Lauro Lines S.R.L. v. Chasser, 490 U.S. 495, 499, 109 S.Ct. 1976, 1978, 104 L.Ed.2d 548 (1989). Furthermore, inasmuch as the immunity argument which AT & T advances is dependent on contract, AT & T is in effect urging that the parties may determine our jurisdiction, a power we are reluctant to recognize.
We think that the potential harm that might be caused by requiring AT & T to await final judgment before it may appeal “does not ‘diffe[r] in any significant way from the harm resulting from other interlocutory orders that may be erroneous ... ’ ” Firestone Tire & Rubber Co. v. Risjord, 449 U.S. 368, 378, 101 S.Ct. 669, 675, 66 L.Ed.2d 571 (1981). Rather, we are satisfied that the right of AT & T, assuming that the parties bargained that resolution of the Business Units disputes must end in the grievance procedure, will be adequately vindicated on appeal at the end of the case in the district court by an order that the resolutions in the grievance procedures are final. That disposition on appeal, though not salvaging AT & T’s trial expenses would certainly vindicate its substantive position and the potential for such a result, while not a perfect remedy for AT & T, precludes jurisdiction under the collateral order doctrine. See Lauro Lines, 490 U.S. at 499, 109 S.Ct. at 1979. Since we find that AT & T’s claimed rights under Article 9 of the Business Units agreement are not equivalent to the qualified immunity in Mitchell and since AT & T can effectively argue the nonjusticiability of the Business Units grievances on appeal from a final judgment of the district court, and obtain meaningful relief, the district court’s order regarding the Business Units grievances does not satisfy the third prong of the Cohen doctrine.
MMS Grievances
AT & T claims that the district court’s decision that the MMS grievances are arbitrable is effectively unreviewable on appeal because arbitrators and another court may treat the district court’s decision on arbitrability as final for purposes of claim or issue preclusion, even though AT & T had not yet had an opportunity to appeal. AT & T posits that CWA could now bring an action to compel arbitration or an action to enforce an arbitration [207]*207award in a state court, based on the district court’s orders.
AT & T’s argument on this point must fail. The district court’s orders did not compel AT & T to arbitrate the subcontracting grievances with the MMS unit. Rather, it held that the grievances are arbi-trable and thus could not be advanced in court. CWA subsequently requested that AT & T arbitrate the grievances and, as AT & T refused, CWA has sought leave in the district court to amend its complaint to compel AT & T to arbitrate these grievances. If AT & T is compelled to arbitrate, the order involved will be subject to eventual appeal. Thus, we do not perceive of any reason to treat this matter differently than a routine action seeking to compel arbitration. However other courts may regard the interim consequences of the interlocutory orders, the arbitration determinations may ultimately be appealed and effectively reviewed and therefore once again the third prong of Cohen has not been satisfied. Furthermore, if AT & T proved to be successful on appeal we think that any order relying on the interlocutory determinations of the district court would be subject to being opened. See, e.g., Fed.R. Civ.P. 60(b)(5).
We also point out that denying collateral finality accords with the policy that orders favoring arbitration over litigation are not immediately appealable. The appealability of arbitration orders under the collateral order doctrine has been described as distorted by “Byzantine peculiarities.” Ballay v. Legg Mason Wood Walker, Inc., 878 F.2d 729, 732 (3d Cir.1989) (quoting New England Power Co. v. Asiatic Petroleum Corp., 456 F.2d 183, 189 (1st Cir.1972)). The November, 1988 amendments to the Arbitration Act, 9 U.S.C. §§ 1-15 “introduce[d] a welcome symmetry” into the law. Ballay, 878 F.2d at 732. Under the amendments to section 15 of the Act, an appeal may be taken from an order refusing a stay of judicial action requested under section 37 or from an order denying a petition to compel arbitration under section 48 or from a final decision with respect to arbitration. Section 15 provides that appeals may not be taken from interlocutory orders granting a stay of action under section 3 or directing arbitration to proceed under section 4. Id. at 731. Thus, section 15 makes clear that with respect to an interlocutory order issued in an ongoing proceeding, any order favoring litigation over arbitration is immediately appealable and any order favoring arbitration over litigation is not. Id.
We regard this case as an ongoing proceeding. The district court’s order dismissing the action to the extent that it concluded the MMS matter was arbitrable is functionally analogous to the grant of a stay in an ongoing proceeding pending the outcome of arbitration. Indeed, as we have indicated, the Union has sought to compel arbitration. Thus, our result advances the laudable policy favoring arbitration over litigation, see Zosky v. Boyer, 856 F.2d 554, 561-62 (3d Cir.1988) (arbitration is an expeditious and inexpensive mode of alternative dispute resolution), cert. denied, 488 U.S. 1042, 109 S.Ct. 868, 102 L.Ed.2d 992 (1989). In the circumstances, the appeal will be dismissed.
III. MANDAMUS
AT & T, in apparent recognition of the jurisdictional problem with its appeal, peti[208]*208tioned this court to issue a writ of mandamus to the district court ordering it to enter judgment in its favor on the Business Units grievances and ordering it to vacate its arbitrability order as to the MMS grievances and to decide the motion for summary judgment as to these grievances. We will deny the petition.
The All Writs Act, 28 U.S.C. § 1651(a), provides that “[t]he Supreme Court and all courts established by Act of Congress may issue all writs necessary or appropriate in aid of their respective jurisdictions and agreeable to the usages and principles of law.” Mandamus may be available if an order is not appealable because it is not final and does not fall within an exception to the finality doctrine. See, e.g., Iowa Beef Processors, Inc. v. Bagley, 601 F.2d 949, 953-54 (8th Cir.), cert. denied, 441 U.S. 907, 99 S.Ct. 1997, 60 L.Ed.2d 376 (1979). Thus, the All Writs Act permits this court to grant relief in limited circumstances, notwithstanding our lack of appellate jurisdiction over a district court’s interlocutory order.
However, due to the “undesirability of making a district court judge a litigant, and the inefficiency of piecemeal appellate litigation” mandamus is limited to extraordinary cases. Mallard v. United States District Court for Southern District of Iowa, 490 U.S. 296, 308, 109 S.Ct. 1814, 1822, 104 L.Ed.2d 318 (1989). Because its use is contrary to the principles of finality, “the writ is seldom issued and its use is discouraged.” Lusardi v. Lechner, 855 F.2d 1062, 1069 (3d Cir.1988). “ ‘The traditional use of the writ in aid of appellate jurisdiction both at common law and in the federal courts has been to confine an inferior court to a lawful exercise of its prescribed jurisdiction or to compel it to exercise its authority when it is its duty to do so.’ ”• Mallard, 490 U.S. at 308, 109 S.Ct. at 1822 (quoting Roche v. Evaporated Milk Ass’n, 319 U.S. 21, 26, 63 S.Ct. 938, 941, 87 L.Ed. 1185 (1943)). Only exceptional circumstances, amounting to a judicial usurpation of power, will justify the invocation of this extraordinary remedy. Allied Chemical Corp. v. Daiflon, Inc., 449 U.S. 33, 35, 101 S.Ct. 188, 190, 66 L.Ed.2d 193 (1980) (per curiam)).
A court may grant the writ upon a showing of two conditions: first, “petitioners must show that they lack adequate alternative means to obtain the relief they seek,” and, second, petitioners must show that their right to issuance of the writ is “clear and indisputable.” Mallard, 490 U.S. at 309, 109 S.Ct. at 1822. The writ may issue when the district court has committed a clear error of law that “at least approaches] the magnitude of an unauthorized exercise of judicial power, or a failure to use that power when there is a duty to do so.” Lusardi, 855 F.2d at 1069.
“[T]he presence of [mandamus] power does not compel its exercise.” Id. at 1070. This court stated in Lusardi that “[e]ven in the presence of a clear error of law which would otherwise escape review and a showing by a party that his right to this relief is ‘clear and indisputable,’ issuance of a writ is within [the court’s] discretion.” Id. The court further admonished that “judges should proceed both carefully and courageously ...” in exercising that discretion. Id.
AT & T asserts that it is appropriate to issue a writ in this case because: (1) the district court committed clear errors of law in construing the Business Units and MMS agreements, which according to AT & T were unambiguous and so involve an issue of law; (2) in the case of the Business Units agreement, the district court exceeded its jurisdiction by agreeing to hear and determine the merits of the Business Units grievances; and (3) in the case of the MMS agreement, the district court wrongfully refused to exercise its jurisdiction by failing to decide AT & T’s motion for summary judgment, which also made it impossible for AT & T to obtain effective and timely review of the court’s decision that the MMS grievances are arbitrable.
The district court denied AT & T’s motion for summary judgment regarding the Business Units grievances as it determined that CWA could obtain a judicial [209]*209determination of the grievances. AT & T claims that Article 9 of the Business Units agreement so clearly and unequivocally provides that the Union had no such right that the district court’s decision to the contrary is a clear error of law resulting in an unauthorized exercise of its judicial power. AT & T argues that unless this court intervenes through mandamus to direct the district court to enter judgment for it, it will suffer the irreparable harm of having to litigate the contracting out grievances in court, denying it the contractual immunity from litigation for which it bargained.
AT & T bases its claim of non-justiciability of the Business Units grievances on Article 9 of the Business Units agreement, which we again quote, in relevant pari:
The Company and the Union recognize and confirm that the grievance procedures set forth in Article 9, and, where applicable, Article 10 (Arbitration) and Article 11 (Mediation), provide the mutually agreed upon and exclusive forum for the resolution and settlement of employee disputes during the term of this Agreement ... Neither the Company, nor the Union ... will attempt by means other than the grievance, arbitration, and/or mediation procedures to bring about the resolution of any issue which is properly subject for disposition through such procedures.
The district court agreed with AT & T that the alleged grievances under the Business Units agreement are not arbitrable, but rejected AT & T’s argument that “the exclusion of [contracting out] grievances from arbitration was intended to operate as a bar to any third party review of the merits of CWA’s claims.” The court stated that the Business Units agreement “contains no provisions, expressed or implied, which can be read to restrict the union’s ability to seek relief through means other than arbitration.”9
There is a strong federal policy favoring judicial enforcement of collective bargaining agreements. Groves v. Ring Screw Works, Ferndale Fastener Division, — U.S. -, -, 111 S.Ct. 498, 501-02, 112 L.Ed.2d 508 (1990). Section 301 of the Labor Management Relations Act “reflects the interest of Congress in promoting ‘a higher degree of responsibility upon the parties to such agreements....’” Id. at -, 111 S.Ct. at 502 (citing Hines v. Anchor Motor Freight, Inc., 424 U.S. 554, 562, 96 S.Ct. 1048, 1055, 47 L.Ed.2d 231 (1976)). The Supreme Court has stated that “under § 301, as in other areas of the law, there is a strong presumption that favors access to a neutral forum for the peaceful resolution of disputes.” Groves, — U.S. at -, 111 S.Ct. at 502.
Despite this policy favoring judicial enforcement, a presumption favoring access to a judicial forum can be “overcome whenever the parties have agreed upon a different method for the adjustment of their disputes.” Id. See also Dickeson v. Daw Forest Products Co., 827 F.2d 627, 629 (9th Cir.1987); Associated General Contractors of Illinois v.. Illinois Conference of Teamsters, 486 F.2d 972, 976 (7th Cir.1973). Section 203(d) of the Taft-Hartley Act, 29 U.S.C. § 173(d), provides that “[f]inal adjustment by a method agreed upon by the parties is declared to be the desirable method for settlement of grievance disputes arising over the application or interpretation of an existing collective-bargaining agreement.” See also Groves, — U.S. at [210]*210-, & n. 10, 111 S.Ct. at 502, & n. 10. However, courts require that preclusion of a judicial determination be set forth clearly and explicitly. See id. at-, 111 S.Ct. at 503; Dickeson, 827 F.2d at 629; Associated General, 486 F.2d at 976.
We will assume but not decide that the district court was wrong in its determination that the claim for the Business Units violations could be asserted in court. Article 9 directly addresses the grievance procedure, and specifically provides that it is the “exclusive forum” for the resolution of grievances and that neither the Company nor the Union will attempt “by means other than the grievance, arbitration, and/or mediation procedures to bring about the resolution of any issue ...” We recognize that inasmuch as the provision is directly concerned with dispute resolution procedures, the words “exclusive forum” and the undertaking that neither party will seek to use other means to resolve disputes arguably precludes resort to court, and thus may overcome the presumption favoring access to a judicial forum.
However, even were we to find that the district court committed a clear error of law, such a finding does not resolve the mandamus issue. Mandamus is a drastic measure and will not be granted if AT & T has an adequate alternative remedy to correct the district court’s error. We find that AT & T has such a remedy.
By denying the petition for the writ we do no more than require AT & T to litigate the contracting out grievances in the district court. But after a final determination regarding the contracting out grievances in that court, AT & T, if aggrieved, can pursue an appeal to this court. At that point, AT & T could again assert its position that the contracting out issue was nonjusticiable and that the grievance process was the final stage for the Union’s complaints. Compare Lusardi, 855 F.2d at 1079 (mandamus granted where there was clear legal error and no adequate remedy because appellate jurisdiction over the issue might have been lost); Carteret Savings Bank, FA v. Shushan, 919 F.2d 225, 233 (3d Cir.1990) (where the writ was issued in the face of a clear legal error because this court’s appellate jurisdiction would have been lost by the failure immediately to correct an erroneous venue transfer).
We recognize that to achieve this remedy, AT & T must litigate the contracting out grievances. However, whatever the outcome of the litigation, the fact that AT & T must bear the inherent costs of litigation is not so consequential a harm that we would be justified in issuing a writ of mandamus to prevent further proceedings. We also point out that we are not favoring a judicial remedy over arbitration as the district court did not hold the Business Units grievances arbitrable. Thus, this is not a case in which a district court has entertained the merits of a labor dispute, disregarding routine arbitration provisions.
Furthermore, this case differs from those in which we intervene in an ongoing proceeding even though there might be a remedy after a trial and thereby avoid retrials. For example, if we granted mandamus to compel a district court to grant a jury trial we might be able to preclude the need for a retrial if on appeal following final judgment we determined that a jury trial had been improperly denied. Thus, in that situation by issuing the writ we could avoid the need for a second trial. On the other hand, in this case if on appeal following final judgment we determine that the court should not have entertained the Business Units claims, a retrial on the merits will not be needed.
We further find that the district court’s decision, even if erroneous, did not rise to a usurpation of judicial power so as to warrant mandamus. There is no question that the district court has jurisdiction over labor disputes under Section 301 of the Labor Management Relations Act, 29 U.S.C. § 185(a). A private agreement between parties cannot divest the district court of jurisdiction granted by Congress; it can only limit the parties’ rights to invoke the court’s jurisdiction.
The district court did not rule on AT & T’s motion for summary judgment on the MMS grievances because it determined [211]*211that the grievances are arbitrable and subject to an exhaustion requirement. AT & T claims that the district court committed a clear error of law in this ruling and it asserts that mandamus is required because AT & T may be unable to obtain effective review on this point. It therefore petitions this court to direct the district court to vacate its order of arbitrability and to rule on its motion that the MMS grievances are nonjusticiable.
As we have indicated, we can grant mandamus if the district court committed a clear error of law and if AT & T has no adequate alternative remedy to correct the district court’s error. Mallard, 490 U.S. at 308, 109 S.Ct. at 1822. We will deny AT & T’s petition because we find that AT & T has an adequate alternative remedy to redress any possible error of the district court. Thus, we discuss but do not definitely decide whether the district court made an error of law in its arbitration decision, though we do conclude it did not make a clear error of law.
The complaint on the contracting out grievances was based on the Bahr-Williams letter which was reprinted in the Memorandum of Understanding between the Union and the Company. This Memorandum was applied to the MMS unit through its collective bargaining agreement with AT & T and the MMS collective bargaining agreement also reprinted the Bahr-Williams letter. The Union’s position was that the Bahr-Williams letter was an agreement not to contract out work and that AT & T had on numerous occasions violated this agreement.
The complaint alleged that the Union had filed grievances with AT & T regarding the contracting out violations but that AT & T denied them. The complaint further stated that “[t]he parties agree that a violation of the Bahr-Williams letter agreement is not subject to arbitration under any of the parties’ collective bargaining agreements ... Therefore, the Union has no recourse other than to seek relief from this Court.” Despite the statement in CWA’s complaint that the contracting out issues were not arbitrable, the district court found that the grievances were, arbitrable and it accordingly dismissed CWA’s claims arising out of the MMS grievances for failure to exhaust the arbitration remedy.
The district court made a two-step analysis to reach its conclusion that the MMS grievances are arbitrable. First, it found that notwithstanding the complaint, the grievances were not based solely on the Bahr-Williams letter, but arose out of the MMS agreement as a whole. Second, it found, and this seems not to be disputed, that this agreement in itself, if correctly construed by the district court with respect to contracting out, did not exclude these grievances from arbitration.
In determining that the MMS grievances derived from the collective bargaining agreement and not the Bahr-Williams letter, the district court relied on this court’s decision in E.M. Diagnostic Systems, Inc. v. Local 169, 812 F.2d 91 (3d Cir.1987), which involved contract provisions similar to those at issue here. In E.M. Diagnostic this court held that a grievance could be said to arise out of a collective bargaining agreement “when the subject matter of the grievance is one that is within the zone of interests that have received protection” in the agreement. 812 F.2d at 95.
In E.M. Diagnostic we found arbitrable a dispute arising under provisions of a collective bargaining agreement that permitted the company to lay off employees only “because of lack of work or for other legitimate reasons in accordance with this Agreement,” requiring the recall of laid off workers according to seniority, and precluding the company from hiring new workers before recalling those who had been laid off. In particular, we found that the provision applied to contracting out grievances, even though the agreement expressly gave the company the right to contract out. In reaching this determination we concluded that the subject matter of the contracting out grievance came within the zone of protected interests under the collective bargaining agreement. Id.
In the present case, the district court found that Paragraph 3 of Article 18 of the MMS agreement, entitled “Movement of [212]*212Personnel,” limited AT & T’s right to lay off employees to situations where “lack of work necessitates decreasing the work force.” The court noted that an arbitrator could find that AT & T’s act of contracting out work evidenced the absence of a lack of work, so that AT & T’s continuance of the layoff would be unjustified if laid off employees were qualified to do the contracted out work. Additionally, the court found that Paragraph 2 of Article 18 set forth a hierarchy of job-related criteria to be used in determining an employee's right to fill a job vacancy. It noted that Paragraph 2.20 states that “new hires” shall be the last category of employees to be given a job and Paragraph 2.4 states that a worker’s status as a laid off employee must not be a factor in determining his right to fill a job vacancy. Therefore, the court found that “[i]t may be that AT & T, by [contracting out] the work at issue, has filled a ‘job vacancy’ with ‘new hires’ in violation of the hierarchy established by Paragraph 2.” 10
Having determined that the MMS grievances arose out of the MMS agreement rather than the Bahr-Williams letter, the district court next considered whether the contracting out grievances were excluded from arbitration under the agreement itself. This was not a difficult question for the guideline principles are clear. While arbitration is a matter of contract and a party cannot be required to arbitrate a dispute which he has not agreed to submit to arbitration, Morristown Daily Record, Inc. v. Graphic Communications Union, 832 F.2d 31, 33 (3d Cir.1987), arbitration is presumed and the courts require arbitration where they are unable definitively to say that a collective bargaining agreement cannot be construed to cover the grievances at issue. AT & T Tech., Inc. v. Communications Workers, 475 U.S. 643, 650, 106 S.Ct. 1415, 1419, 89 L.Ed.2d 648 (1986). Thus, “[i]n the absence of any express provision excluding a particular grievance from arbitration ... only the most forceful evidence of a purpose to exclude the claim from arbitration can prevail .... ” United Steelworkers of America v. Warrior & Gulf Navigation Co., 363 U.S. 574, 584-85, 80 S.Ct. 1347, 1354, 4 L.Ed.2d 1409 (1960). The district court found that neither the inclusion of the Bahr-Williams letter in Part II of the MMS agreement nor the agreement itself satisfied this forceful evidence requirement. In this regard we point out that AT & T does not contend that grievances under Article 18 are not subject to arbitration. Rather, it asserts that Article 18 is not in issue here as it is not concerned with contracting out. While we do not definitely endorse or reject the district court’s reasoning that the MMS grievances are arbitrable, we do conclude that the court did not commit a clear error of law in its conclusions.11
In any event we must deny the writ because we find that AT & T has an adequate alternative remedy to redress any error of the district court. AT & T claims that it does not have an adequate alternative remedy because, “[ajlthough the holding [that the MMS grievances are arbitra-ble] would in theory be reviewable upon appeal of a final order at the conclusion of this action, by that time the CWA may very well have received arbitration awards— both with respect to the grievances which were the subject of the CWA’s Complaint and future grievances.” AT & T claims that the determination that the subcontracting grievances are arbitrable could be held final for purposes of claim or issue preclusion, even though not final for purposes of 28 U.S.C. § 1291. AT & T posits that the Union could now bring an action to compel arbitration or an action to enforce an arbitration award in a state court, based on the district court’s order.
[213]*213We reject this argument. The district court did not compel AT & T to arbitrate the subcontracting grievances with the MMS unit. Rather, it found the grievances arbitrable. CWA subsequently requested that AT & T arbitrate the grievances and AT & T refused. CWA has since sought leave to amend its complaint in the district court seeking to compel AT & T to arbitrate these grievances. If the district court orders AT & T to arbitrate, that decision can ultimately be appealed to this court, so that AT & T would have an adequate remedy. This court would not lose jurisdiction over the appeal.
We find AT & T’s argument regarding the preclusive effect of the district court’s order unconvincing. We are more persuaded by the reasoning of the court of appeals in Timberlake v. Oppenheimer & Co., Inc., 729 F.2d 515 (7th Cir.1984), in which the court refused to issue a writ as to a district court’s order to arbitrate, rejecting the argument that arbitration would work as res judicata or a collateral estop-pel bar to the right to a jury trial on the non-arbitrable issues outstanding. The court noted that this argument “confuses the merits of an appeal with the issue of appealability.” Id. at 519. The court stated that “if the district court erroneously ordered arbitration, the error can be corrected on appeal from a final order of the district court confirming the arbitration award or otherwise disposing of the litigation.” Id. The court recognized the principle under which the erroneous denial of a demand for a jury trial can be corrected immediately through a writ of mandamus, but stated that “this principle has not been pushed so relentlessly as to allow an immediate appeal from every type of order that might result in a party’s right to a jury trial being diminished by operation of res judicata or collateral estoppel.” Id. Similarly, in this case, if the district court’s decision on arbitrability is erroneous it can be corrected on appeal from a final decision of the district court compelling arbitration or otherwise disposing of the litigation. Furthermore, as we have already noted, if AT & T proved to be successful on appeal we believe that any order relying on the interlocutory determinations of the district court could be opened. See, e.g., Fed.R. Civ.P. 60(b)(5).
Thus, AT & T has an adequate alternative remedy in its ultimate right to appeal to this court from the district court’s order that the MMS grievances are arbitrable. The fact that AT & T may have to arbitrate before taking this appeal is not a basis for mandamus. Compare Carteret Savings Bank, FA v. Shushan, 919 F.2d at 233 & n. 15 (issuance of the writ appropriate for the district court’s improper transfer of a case under 28 U.S.C. § 1406(a) over plaintiff’s objection because, once the transfer occurred, this court would lose jurisdiction and there would be no adequate remedy to appeal in this circuit). The issue of whether AT & T has an adequate alternative remedy to mandamus is similar to the issue of whether the district court’s order regarding the arbitrability of the MMS grievances could be effectively reviewable upon final judgment under the collateral order doctrine. As discussed above, an order to arbitrate is generally not immediately reviewable under the collateral order doctrine because of federal policy favoring arbitration over litigation. See generally 9 U.S.C. §§ 1-15. We find that this policy also supports the denial of the writ in this case.
CONCLUSION
The district court order does not meet the third prong of the collateral order doctrine and we therefore will dismiss AT & T’s appeal. We will also deny the petition for mandamus.