Detroit ? More progress was reported Saturday as negotiators for General Motors Corp. and the United Auto Workers worked on a historic new contract that would shift retiree health care costs from the company to the union.

Two people who have been briefed on the talks said Saturday that bargainers were getting closer to reaching a deal on the company funding a union-run trust that would take over much of GM’s $51 billion unfunded obligation to pay health care costs for retirees and current workers after they retire.

The people, who requested anonymity because the talks are private, said they were told negotiators are optimistic a tentative deal on the entire contract could be reached as early as today or Monday. Any agreement would have to be ratified by GM’s 73,000 UAW members.

GM spokesman Tom Wickham said the talks began midmorning Saturday and recessed Saturday evening. They were to resume this morning.

The UAW has picked GM as the lead company and potential strike target, so Ford Motor Co. and Chrysler LLC would likely match many of the terms of GM’s agreement.

One of the people briefed on the talks said early Saturday that the two sides had not agreed on how much GM would have to kick into the trust, called a Voluntary Employees Beneficiary Association or VEBA. Neither person knew if that had changed by late Saturday afternoon.

“They said they were real close,” one of the people said.