CHICAGO - United Airlines' mechanics rejected a tentative contract agreement and voted to authorize a strike if the carrier persuades a bankruptcy judge to impose the labor cuts, union officials said Friday.

The vote is a setback in United's bid to cut costs in order to exit bankruptcy. The company said Friday that it would to ask a bankruptcy judge to impose the wage and benefit cuts on mechanics, which would save about $100 million annually.

"Regretfully, we will be seeking to reject the current contract to achieve the savings we need," the company said in a statement.

The Aircraft Mechanics Fraternal Association represents about 7,000 United mechanics. The union said members "overwhelmingly" rejected the contract, although it did not release vote totals.

"The employees have shown that they do not have faith in the company's ability to successfully return United Airlines to profitability," O.V. Delle-Femine, AMFA's national director, said in a statement. "Our members are tired of subsidizing mismanagement."

The union said the cuts total more than 18 percent when reductions in benefits such as sick time and holidays are factored in.

United is seeking to rewrite all its labor contracts to save costs for the second time in its 26-month bankruptcy. After slashing labor costs by $2.5 billion annually in 2003, the airline now says it needs another $725 million in yearly reductions.

Analysts said the cuts by United, a unit of Elk Grove Village, Ill.-based UAL Corp., risk alienating employees and could even threaten the airline's survival if it seeks to impose them by court order. Eastern Airlines went out of business in 1991 after its mechanics went on strike rather than accept sharply reduced wages in bankruptcy.

But it is unclear whether the union can legally strike under rules of the national Railway Labor Act, which governs airline contracts.

"We think the employees represented by AMFA are not legally permitted to take that action," United spokeswoman Jean Medina said. "We will take whatever action is necessary to prevent any potential disruption of our operations."

AMFA spokesman Richard Turk said the union's legal team believes it does have the right to strike if a judge replaces the union's contract.

George Novak, an airline industry researcher at George Washington University's Aviation Institute, said he thinks it's unlikely AMFA would strike. He said disruptive labor actions such as sickouts are more likely, which could bring closer scrutiny from the Federal Aviation Administration (news - web sites) on safety and maintenance compliance.

"United needs all good news right now to emerge from bankruptcy, and this is not good news," Novak said.

He said the vote should send a message to the beleaguered airline industry that there are limits to the number of times it can rework labor agreements in order to stem large losses.

"I think this shows the industry that at some point these unions have got to say no; the airlines can't keep going back and saying, 'You've got to take another cut,'" Novak said.

United mechanic Dave Quinn, who sat in on the negotiations, said United officials rejected a union proposal agreeing to wage cuts provided they could be refunded in the future if fuel costs or pressure on fares eased.

"They have made the bogey man out to be fuel prices and weak revenue, so we offered them a loan to bridge the current financial crisis," said Quinn, who has worked as a United mechanic in Chicago for 20 years. "As soon as revenues increase or fuel costs go down, we'd see some payback."

Quinn said United's rejection of that proposal swayed many members to vote against the contract.

Darryl Jenkins, a professor of airline management at Embry Riddle Aeronautical University at Daytona Beach, Fla., said AMFA's strike threat eventually could scare away some United customers.

"I always take what these (union) guys say seriously because the threat itself is enough to cause passengers to book away," Jenkins said.

United pilots and flight attendants are conducting similar contract ratification votes, with the results to be announced Monday. Members of the Air Line Pilots Association (news - web sites) are weighing an 11.8 percent pay cut. Details of the Association of Flight Attendants tentative deal have not been disclosed.

The union representing baggage handlers, ramp workers and public-contact workers faces an April 11 deadline for negotiating a pact after a short-term deal was put in place this month.

The nation's No. 2 carrier also wants to eliminate its traditional pension plans and replace them with defined-contribution plans, a move that has inflamed unions and prompted dismay from the federal Pension Benefit Guaranty Corp., which would be expected to take responsibility for up to $6.4 billion of United's pension liabilities.