Negotiators for the United Auto Workers union and the three large U.S. automakers — General Motors, Ford Motor and Stellantis, the parent of Chrysler, Jeep and Ram — remained far apart as a limited strike began on Friday.

The strike is not a full-scale walkout by the union’s roughly 150,000 members but a “limited and targeted” work stoppage by about 12,700 workers that could expand if talks remain bogged down. It began after workers’ four-year contracts expired.

The union must negotiate separate deals with each of the companies on issues including pay and retirement benefits.

The U.A.W. has demanded a 40 percent wage increase over four years — an amount that union officials said matches the raises the top executives at the three companies have received over the last four years. Those raises are also meant to compensate for more modest increases the autoworkers received in recent years and the concessions the union made to the companies after the 2008 financial crisis.

The union is also seeking cost-of-living adjustments that would nudge wages higher to compensate for inflation. And it wants a reinstatement of pensions for all workers, improved retiree benefits and shorter work hours, as well as and an end to a tiered wage system that starts new hires at much lower wages than the top U.A.W. pay of $32 an hour.

As of last Friday, the companies offered to raise pay by around 14.5 percent to 20 percent over four years. Their offers include lump-sum payments to help offset the effects of inflation, and policy changes that would lift the pay of recent hires and temporary workers, who typically earn about a third less than veteran union members.

It was not clear how much progress the union and the companies have made on the other issues.

The companies say that they are investing billions in a transition to battery-powered vehicles, which makes it harder for them to pay substantially higher wages. They say they are at a disadvantage compared with nonunion automakers like Tesla, which dominates the sales of electric cars.

On Thursday, G.M. said in a statement that it had made a new offer to the union and that the company was engaged in “continuous, direct, and good faith negotiations” in an effort to avoid a strike.

Declaring that “the future of our industry is at stake,” Ford said on Wednesday that it was “ready to reach a deal,” adding, “We should be working creatively to solve hard problems rather than planning strikes and P.R. events.”

Stellantis said on Wednesday that its “focus remains on bargaining in good faith to have a tentative agreement on the table before tomorrow’s deadline.”

In a 40-minute address on Wednesday, the union’s president, Shawn Fain, called the automakers’ offers “insulting.”

“For the last 40 years, the billionaire class has been taking everything and leaving everybody else to fight for the scraps,” he said. “We are not the problem. Corporate greed is the problem.”

The union plans to pay striking workers $500 per week and cover the cost of their health insurance premiums. The union’s $825 million strike fund is big enough to cover payments to workers in a full strike against all three companies for about three months — although the U.A.W. has said it would expand the limited stoppage only if talks bogged down.

Only certain models of cars are affected right now, but if the strike lasts long enough to start impacting inventories, car dealers will have fewer vehicles on their lots and may start pushing up prices on the ones they do have.

This comes at a time when car prices had already been rising, and the average interest rates on auto loans had been climbing — making it harder for buyers to afford cars.