NEW YORK (CNN/Money) - United Airlines is prepared to go to bankruptcy court soon after Christmas to start the process to void its labor contracts if it doesn't reach agreement on deep concessions from its unions.

The world's No. 2 airline, which filed for bankruptcy court protection on Dec. 9, said its preference is to reach agreements with the unions, not seek court action. But it said it would file a motion Dec. 26 to change the contracts if it doesn't reach agreement.

It seemed to acknowledged it would not have new agreements in place by that point, but said it would continue to negotiate "in good faith" with the unions on new wage deals after making the court filing.

"While United will continue to work collaboratively with its unions, the filing of this motion would be necessary to ensure that United remains in compliance with the financial requirements of the company's debtor-in-possession (DIP) financing agreements by seeking the court's assistance should the company and the unions fail to reach consensual agreements," said the company's statement.

The airline has lined up $1.5 billion in financing to take it through bankruptcy reorganization, but has only closed on $800 million of that package. The rest is contingent on the airline reaching agreement with the union on cost reductions.

Union officials did not seem surprised by the move. In a statement, the Air Line Pilots Association described the filing as "purely procedural", and the International Association of Machinists described United's announcement as "an expected part of the bankruptcy process" in a letter to members.

However, the pilots' union added that United's actions in negotiations so far "gives us pause and concern," and said the company had not provided the union with information about its business plan.

Association of Flight Attendants spokeswoman Sara Dela Cruz said the filing will not stop the company's unions from trying to reach a new labor agreement with United management.

"This is not a shock to us," she said. "We're still committed to working outside of the bankruptcy court process with the company."

The AFA says that United is seeking $2.4 billion in annual cost savings from labor and that the unions will work to lessen that amount of cuts. The IAM has told members that United's proposal is for a 13 percent wage cut, and changes in job protection language, such as a requirement that heavy maintenance of aircraft be done inside the United States and that the company can't sell or lease out its major maintenance facilities.

United would not comment on the $2.4 billion cost saving target. That cut would be about 150 percent more than it had negotiated with the union leadership in annual cost savings before the bankruptcy filing. But the IAM unit that represents mechanics and ground workers voted against even that more modest concession package, despite strong lobbying by union leadership and the threat it could bring on bankruptcy.

An ALPA spokesman said Monday that the pilots union was looking at the new proposed cost cut but couldn't commit to it without seeing the company's entire business plan.

Shares of UAL (UAL: Research, Estimates) lost 23 cents, or 15 percent, to $1.27 in trading Tuesday, although shares rose 11 cents in after-hours trading.