Detroit ? General Motors Corp. and the United Auto Workers made progress at the bargaining table Saturday but still faced significant hurdles and ended negotiations for the day without reaching an agreement.

Negotiations ended about 8 p.m. CDT, GM spokeswoman Katie McBride said. They are scheduled to resume midmorning today.

Some union subcommittees – which handle issues such as pensions, benefits and job security – have wrapped up talks, but an agreement wasn’t expected Saturday because negotiators were still dealing with some key issues, according to a person who was briefed on the negotiations.

The person, who spoke on condition of anonymity because the talks are private, also confirmed that GM Chairman and Chief Executive Officer Rick Wagoner and UAW President Ron Gettelfinger are actively involved in the discussions.

Several local union officials who have been in touch with bargainers said the talks are going well but the outstanding issue is retiree health care expenses. GM wants the union to take over responsibility for retiree health care costs using a company-funded trust and the union was asking for job guarantees in exchange for taking on the costs.

The local officials spoke on condition of anonymity because they weren’t authorized to speak publicly about the talks.

GM’s 73,000 U.S. auto workers were without a contract as of midnight Friday and could go on strike at any time if negotiations break down. In Spring Hill, Tenn., hundreds of union members were at the local UAW hall Saturday, waiting for news.

“Members are very apprehensive. These are historic times and everybody realized that,” said UAW Local 1853 President Mike O’Rourke.

Some other union halls were quiet as local leaders prepared for membership meetings or awaited word from the UAW. In Lansing, UAW Local 652 President Chris “Tiny” Sherwood said he was keeping the hall open and making sure members were ready if a strike was called.

A message was not returned Saturday for UAW spokesman Roger Kerson.

Five of GM’s 18 U.S. assembly plants were operating Saturday, GM spokesman Tom Wickham said, including two plants in the Lansing area and one each in Flint, Wentzville, Mo., and Lordstown, Ohio. Only two plants in Flint and Lansing were scheduled to be running today.