In separate statements Tuesday, Sprint and WorldCom noted the Justice Department's opposition to the merger. WorldCom said it will "promptly review its options with Sprint."

Sprint said it is "disappointed" that it hasn't been able to convince the Justice Department that "the merger is in the best interest of the American public and would advance competition."

The proposed linkup already faces scrutiny in Europe, where the European Union's competition commissioner said on Monday in Washington that the planned acquisition wouldn't be allowed in its present form. Speaking to reporters, Mario Monti said the European Commission would consider additional conditions in "exceptional circumstances" and if those conditions didn't need market testing.

EU competition regulators opened an in-depth probe into the merger pact - then valued at around $120 billion - in February, citing concern about Internet backbone access, global telephony services to multinationals and long-distance telephony.The companies already have offered to sell Sprint's Internet business. But Monti has indicated that the commission would prefer MCI WorldCom to divest itself of its UUNet Internet business, partly because UUNet is a stand-alone business whereas Sprint's Internet activities are an integral part of the rest of its business.

WorldCom chief executive Bernie Ebbers has so far ruled out selling UUNet. Sprint has already sold its stake in its Global One venture with European carriers Deutsche Telekom AG and France Telecom, but this wasn't enough to win antitrust approval.