PITTSBURGH — Alcoa and the United Steelworkers reached a tentative agreement on a four-year contract late Wednesday, avoiding a strike by 9,000 workers at 15 of the aluminum company's U.S. plants, an Alcoa spokesman said.

The deal was reached less than two hours before the contract expired at midnight in St. Louis, where the negotiations were taking place, Alcoa spokesman Kevin Lowery said from the company's offices in Pittsburgh. Union officials could not immediately be reached for comment.

The deal averts what would have been the union's first strike since 1986. Alcoa planned to issue a more detailed statement this morning, Lowery said.

He said the deal requires the workers to pay part of their health insurance premiums for the first time, reportedly a major sticking point in the negotiations.

Retirees covered under the deal will continue to receive medical coverage. The deal also includes a new pay-for-performance program, and includes a new skills assessment and worker training programs, Lowery said.

No other details of the deal were immediately available.

DETROIT — Ford Motor Co. on Wednesday asked a federal judge to approve a health care agreement with the United Auto Workers that would save the company $200 million annually by making retired autoworkers pay more for their health care.Mark Baumkel, an attorney who represents 430 retirees opposed to the deal, said the UAW lacks the legal authority to change retirees' health care. Baumkel also rejected Ford's contention that the deal will cover health care costs for 20 years, pointing out that the company is allowed to renegotiate the terms in 2011.Ford says the agreement will shave $5 billion off its overall health care liability, which is currently estimated at $35 billion.The settlement would require retirees to pay deductibles and co-payments for the first time, up to $752 annually for families and $370 for individuals. Active workers approved the deal late last year by a 51 percent margin, but UAW retirees weren't allowed to vote. The agreement is similar to one at General Motors Corp. approved earlier this year by a different federal judge.