CHICAGO, Dec. 31 (UPI) -- Unionized mechanics and ground workers at United Airlines went to bankruptcy court Tuesday to challenge the airline's bid to void labor contracts and impose a temporary 13 percent pay cut.

United has warned of more layoffs and said it expects to lose a record $3.2 billion in 2002, surpassing the previous estimate of $2.5 billion.

United is seeking $2.4 billion a year in wage and benefit cuts from its five unions to meet strict cash-flow requirements imposed by lenders providing $1.5 billion in debtor-in-possession financing. Pilots, flight attendants, flight dispatchers and meteorologists have tentatively agreed to short-term pay cuts of 9 percent to 29 percent, but the International Association of Machinists and Aerospace Workers -- which represents 37,000 mechanics and ground workers -- rejected the give-backs.

IAM filed a motion objecting to United's effort to impose wage cuts under Section 1113 of the U.S. Bankruptcy Code.

"The IAM today filed its objection to United's 1113 (e) application ... " a release posted on the union's Web site said. "The permanent cost savings United Airlines is seeking from its employees goes far beyond the temporary wage reductions."