Greyhound Lines said it might terminate a merger.

The company threatened to scuttle its merger with Trailways Lines unless the government allows a Greyhound affiliate to immediately take over Trailways’ operations. In a filing with the Interstate Commerce Commission, Greyhound said that Trailways could collapse “in a matter of days� unless the two bus lines are allowed to operate together immediately. The Justice Department has asked the ICC to defer action until it is determined whether Trailways qualifies as a “failing firm� under antitrust laws. Under the failing firm doctrine, the company to be purchased must show that it will be unable to meet financial obligations with existing assets. It also must establish that no other firm representing less of a threat to competition is willing to buy the assets.