A top United Auto Workers official said the union and General Motors are far apart on major issues, increasing the likelihood of a strike as early as Sunday night.
The union, in letters to members and GM Saturday, said it will let its four-year contract with the company expire just before midnight. But workers are to report to their jobs if they're scheduled to work on Sunday.
Just what the union will do after that will be decided in meetings scheduled for Sunday morning in Detroit.
"If they're not extending the agreement, then that would leave them open to strike," said Kristin Dziczek, vice president of the Center for Automotive Research, an industry think tank. "They can strike once the contract has expired."
The letters are designed to turn up the pressure on GM negotiators as the contract expiration deadline approaches at 11:59 pm on Saturday.
"While we are fighting for better wages, affordable quality health care, and job security, GM refuses to put hard working Americans ahead of their record profits of $35 billion in North America over the last three years," union vice president Terry Dittes said in a statement. "We are united in our efforts to get an agreement our members and their families deserve."
But GM, in a statement on Saturday night, still held out hope for an agreement, saying it continues to work on solutions to difficult challenges.
"We are prepared to negotiate around the clock because there are thousands of GM families and their communities - and many thousands more at our dealerships and suppliers - counting on us for their livelihood. Our goal remains on building a strong future for our employees and our business," the GM statement said.
Dittes, the union's chief bargainer with GM, wrote in the letter to local union leaders that both sides are far apart on nearly all important economic issues after months of bargaining.
"We still have many outstanding issues remaining, including significant differences between the parties on wages, health care benefits, temporary employees, job security and profit sharing," the letter said.
The move by the union also comes as it faces an internal struggle over a federal corruption investigation that has touched its leader, President Gary Jones.
Plant-level union leaders from all over the country will be in Detroit on Sunday to talk about the next steps, and after that, the union likely will make an announcement.
But leaders surely will face questions about an expanding federal corruption probe that snared a top official on Thursday. Vance Pearson, head of a regional office based near St. Louis, was charged with corruption in an alleged scheme to embezzle union money and spend cash on premium booze, golf clubs, cigars and swanky stays in California. It's the same region that UAW President Gary Jones led before taking the union's top office last year.
Jones has not been charged.