With only three days to go before a potentially crippling strike, United Airlines on Monday announced it had reached a tentative contract agreement with the union representing its 12,800 mechanics and aircraft cleaners.

The International Association of Machinists and Aerospace Workers confirmed the tentative settlement. Details were not immediately disclosed.

The announcement came on the fourth day of urgent talks following the mechanics' rejection of United's contract offer last Tuesday. The mechanics were preparing to walk off the job at 12:01 a.m. EST Wednesday if no settlement was reached, grounding the world's second-biggest airline.

"Our negotiating team and United's labor committee of the board of directors have accepted the terms of the IAM's proposal," Jack Creighton, chairman and chief executive of United parent UAL Corp., said in a prepared statement. "With the agreement, our customers can be confident that United will continue to operate without disruption."

Despite Creighton's repeated assurances that he was confident an agreement would be reached, United had acknowledged a decline in bookings for the coming days, reflecting public fears of a shutdown.

United Airlines  posted a net loss of $2.1 billion in 2001, an industry record, and before the announcement of the deal Crain's Chicago Business reported Monday that the company was in consultations with its law firm's bankruptcy specialists.

Negotiators for the two sides held talks through the weekend in a hotel in suburban Rosemont, Ill., near both O'Hare International Airport and UAL headquarters.

Mechanics over the weekend began removing their tool boxes and personal belongings from United maintenance centers in preparation for a strike.

The airline said the International Association of Machinists will forward details to membership for a vote within the next two weeks.

United said the tentative deal means its jets will continue to operate without disruption.

The Associated Press contributed to this report.