The three Detroit automakers and the United Auto Workers union have begun negotiating a brand new labor contract in what might develop into probably the most contentious talks between the 2 sides in maybe half a century.

The discussions, which formally began on Thursday, come as General Motors, Ford Motor and Stellantis have posted a protracted streak of robust earnings in North America, and after the U.A.W. elected a president who has vowed to win again most of the wage and profit concessions the union has ceded during the last 20 years.

Shawn Fain, an outsider candidate, prevailed in an upset election victory over the incumbent U.A.W. president this yr largely by promising to take a extra militant strategy to contract negotiations than his latest predecessors. Since then, he has expressed a readiness to close down factories to attain the targets of the union, which represents 150,000 hourly staff employed by the three Detroit firms.

“If the Big Three don’t give us our fair share, then they are choosing to strike themselves,” Mr. Fain, 54, mentioned Wednesday as he greeted staff ending their shift at a G.M. electrical car plant in Detroit. “We are not afraid to take action. Our union is united. We can’t be afraid to stand up and fight.”

A day later, Mr. Fain underscored his view by breaking with custom and declining to participate within the typical ceremonial opening of negotiations, the place prior to now the U.A.W.’s president shook arms with the automakers’ chief executives as a gesture of concord for photographers and tv cameras earlier than the 2 sides bought right down to bargaining.

“I’m not shaking hands with any C.E.O.s until they do right by our members and we fix the broken status quo,” Mr. Fain mentioned.

The bargaining is happening because the labor motion is displaying renewed power within the United States. A strike by Hollywood writers in opposition to film and tv producers simply entered its third month. Hollywood actors went on strike on Friday. Graduate pupil academics — some represented by the U.A.W. — have been on strike at universities throughout the nation since April. Hotel workers in Los Angeles walked off the job for 3 days in June.

In the previous few years, greater than 300 Starbucks shops in addition to some Trader Joe’s shops, Chipotle eating places and an Amazon warehouse in New York have unionized. The Teamsters union is threatening to strike against UPS in August if the 2 can not agree on a brand new contract.

“We are seeing in very diverse workplaces a new interest in unions and a willingness to strike,” mentioned Harley Shaiken, a professor emeritus on the University of California, Berkeley, who has adopted the labor motion for greater than three many years. “What we don’t know yet is how large this movement is going to become and how far it is going to go.”

The negotiations coincide with the beginning of the 2024 presidential election marketing campaign. The U.A.W. historically backs the Democratic candidate, however the union has withheld an endorsement of President Biden to push the White House to up its help of unions.

In Detroit, the contract talks are enjoying out amid a momentous transition to electrical automobiles. G.M., Ford and Stellantis have been investing billions of {dollars} in new applied sciences and battery vegetation, though to date they’ve launched solely a handful of recent E.V.s, gross sales of those automobiles are rising however low, and not one of the three automakers has but made cash off E.V.s.

This transition presents a priority for the union as a result of E.V.s have far fewer components than standard autos — they don’t have any exhaust system, no transmission, no gas system — and require fewer staff to provide them. G.M., Ford and Stellantis have began constructing battery vegetation with joint-venture companions, which aren’t routinely coated by the U.A.W.’s labor contract.

The union has organized a G.M. battery plant in Ohio, however staff there should negotiate their wage charges and phrases individually from the primary U.A.W. settlement.

“Electrification presents problems,” mentioned Earl Fuller Jr., the G.M. chairman at Local 160 in Warren, Mich. “We see jobs going away, and that needs to be addressed.”

While investing closely in E.V.s, the automakers are nonetheless producing substantial earnings off gross sales of pickup vehicles and sport utility automobiles, helped by near-record costs of recent automobiles. Over the final 10 years, G.M. and Ford have usually made a pretax revenue of $7 billion to $11 billion a yr in North America. Stellantis, the smallest of the three, has normally earned considerably much less, though its pretax ends in the area topped $13 billion in 2021 and 2022.

Mr. Shaiken mentioned the union had appreciable leverage within the negotiations. “The stakes are very high for the auto manufacturers with this E.V. transition taking place,” he mentioned. “A strike could be very costly for the companies.”

In his estimation, a strike is probably going however not sure.

The automakers keep that they bear a drawback in labor prices. According to Ford, its hourly value of U.A.W. labor is $64, and it estimates that’s $9 greater than the labor value for foreign-owned automakers with nonunion vegetation within the United States, and $14 to $19 greater than that of Tesla, which additionally makes use of nonunion staff.

In an announcement, Ford famous that it had 57,000 hourly U.A.W. staff, greater than its two Detroit rivals, and that it produced extra automobiles within the United States than the others as properly.

“We look forward to working with the U.A.W. on creative solutions during this time when our dramatically changing industry needs a skilled and competitive work force more than ever,” the corporate mentioned.

Stellantis mentioned it aimed to barter a contract that ensured its future competitiveness in addition to good wages and advantages. “Together, we must approach these negotiations with open minds,” the automaker mentioned.

In the previous, G.M., Ford and Stellantis have typically misplaced cash, or made little. Each wanted concessions from the union to outlive, and the union steadily agreed to most of the automakers’ calls for in a collection of contracts starting in 2003.

The value of well being take care of U.A.W. retirees has been shifted from the automakers to a union belief fund. The union agreed to permit the producers to begin new hires at about half the $32 hourly price that veteran staff earn. New staff get 401(okay) accounts for retirement as a substitute of assured pensions. While the producers have been paying substantial profit-sharing bonuses — typically greater than $10,000 for every employee — the U.A.W. has gone with out cost-of-living changes that previously protected staff from inflation.

In contract talks 4 years in the past, the union sought to regain floor on these points. The automakers agreed to will increase in hourly wages and profit-sharing, improved phrases for non permanent staff and modified wage tiers however stopped in need of scrapping them for a single wage price.

Workers at G.M. additionally demanded that the corporate reverse a plan to shut a manufacturing facility in Lordstown, Ohio, and went on strike for 40 days however ended up ratifying a contract that allowed the shuttering of the plant.

The 2019 contract did embody provisions for G.M. to speculate $3 billion in its plant in Detroit, which had additionally been designated for potential closing. The cash was used to transform the positioning into G.M.’s flagship E.V. plant, now known as Factory Zero, which produces an electrical Cadillac S.U.V. in addition to the electrical GMC Hummer.

Margaret Hudgins-Washington, 56, a battery operator on the plant, was one in all a number of dozen who stopped to speak to Mr. Fain on Wednesday. She has labored there for a few yr, makes about $16 an hour and desires to see an finish to the two-tier wage construction.

“Our workers have regressed with inflation,” she mentioned. “So I think we need better pay.”

She and lots of others uniformly endorsed Mr. Fain’s harder strategy.

“I think he’s doing the right thing,” mentioned Kevin Winston, an electrician and a father of 5 from Brownstown, Mich. “Now is the time. I’m ready to strike, 100 percent, and I haven’t heard any people say we shouldn’t strike.”