Autoworkers walked off the job on Friday at three factories that produce a few of the Detroit carmakers’ hottest autos, the opening salvos in what might change into a protracted strike that hurts the U.S. economic system and has an affect on the 2024 presidential election.

Almost 13,000 members of the United Auto Employees at vegetation in Ohio, Michigan and Missouri joined early Friday in what the union described as a focused strike that would increase to extra vegetation if its calls for for pay raises of as much as 40 p.c and different features weren’t met.

The union’s four-year contracts with three automakers — Common Motors, Ford Motor and Stellantis, which owns Chrysler, Jeep and Ram — expired Thursday, and the businesses and the union remained removed from placing new offers.

The U.A.W.’s president, Shawn Fain, used sweeping language on Thursday to explain why his members have been happening strike in opposition to all three automakers on the similar time — one thing the union had by no means finished in its almost 90-year historical past.

“That is our technology’s defining second,” Mr. Fain, the union’s first chief elected instantly by members, mentioned in a web based video. “The cash is there, the trigger is righteous, the world is watching, and the U.A.W. is able to arise.”

The union and the businesses didn’t negotiate on Friday, however the U.A.W. mentioned it deliberate to renew bargaining on Saturday. President Biden dispatched two senior administration officers to Detroit on Friday to encourage the businesses and union to achieve agreements.

At a Ford plant in Wayne, Mich., west of Detroit, strikers waved placards — one learn, “Report Income; Report Contracts” — and gave thumbs-up to honking autos. A metallic signal on a chain-link fence learn, “Completely NO international vehicles allowed.” The protesters have been assigned to a six-hour shift on the picket line. If the strike continues, they are going to be referred to as to at least one shift per week.

Whereas at the start a battle between autoworkers and automakers, the battle might have far-reaching penalties. A prolonged strike would cut back the variety of new vehicles obtainable on the market, which might gasoline inflation and pressure the Federal Reserve to maintain rates of interest excessive.

A strike additionally presents a quandary for Mr. Biden, who has referred to as for rising incomes however should even be aware of the strike’s financial affect and his objective to advertise electrical autos as an answer to local weather change.

Talking on the White Home on Friday, the president strongly supported the union. “Over the previous decade, auto corporations have seen report income, together with in the previous couple of years, due to the extraordinary talent and sacrifices of U.A.W. staff,” he mentioned. “However these report income haven’t been shared pretty.”

The U.A.W. says its pay calls for roughly correspond to the will increase within the compensation of the highest executives at Ford, G.M. and Stellantis. The raises are additionally meant to assist compensate staff for the bottom they’ve misplaced to inflation and massive concessions the union made to the automakers after the 2007-8 monetary disaster, when G.M. and Chrysler have been compelled to restructure themselves in chapter courtroom.

However auto executives say they already pay manufacturing staff considerably greater than rivals, like Tesla and Toyota, whose U.S. staff are usually not unionized. The businesses additionally contend that such large raises would undermine their efforts to develop electrical autos and stay related because the trade makes a troublesome and dear shift from gasoline vehicles and vans to electrical autos.

If unions obtained all that they have been asking for, “we must cancel our E.V. investments,” Jim Farley, the chief government of Ford, mentioned in an interview on Friday. As an alternative, Ford would wish to focus on giant sport utility autos and pickups that generate essentially the most revenue, he mentioned.

Ford, which employs essentially the most union members, reported a revenue of $1.9 billion within the second quarter, equal to 4 p.c of its gross sales. Tesla made $2.7 billion in the identical interval, about 11 p.c of its gross sales.

Mr. Farley sounded pessimistic in regards to the possibilities of agreeing on a contract quickly. “They aren’t negotiating in good religion if they’re proposing offers that they know are going to crater our investments,” he mentioned.

Mr. Fain’s resolution to close down simply three factories is a departure for the union, which in earlier strikes sometimes walked out of all of the factories of a single automaker. By interrupting manufacturing of a few of the most worthwhile autos, whereas permitting most vegetation to maintain working, the union hopes to inflict ache on the carmakers whereas permitting most of its members to proceed gathering paychecks.

However it could be troublesome for the union to restrict the harm to its members’ incomes. Ford advised staff at a facility in Michigan, who weren’t on strike, to remain house Friday due to elements shortages brought on by the strike. G.M. mentioned it might most likely lay off 2,000 staff at a manufacturing facility in Kansas subsequent week due to an absence of elements produced on the manufacturing facility close to St. Louis that’s on strike.

Fewer than 10 p.c of the almost 150,000 U.A.W. members on the three corporations are on strike. Restricted strikes might permit the union to take care of the strain longer by preserving its strike fund of $825 million. The union can pay placing staff $500 per week and canopy their medical insurance premiums.

Along with the Ford plant in Michigan, which makes the Bronco and the Ranger pickup truck, and the G.M. plant in Wentzville, Mo., which makes the GMC Canyon and the Chevrolet Colorado, staff shut down a Stellantis complicated in Toledo, Ohio, that makes the Jeep Gladiator and Jeep Wrangler. If no settlement is reached, the union is predicted to focus on extra factories in weeks to return.

The union can also be looking for cost-of-living changes that might defend staff if inflation flares up once more. And it needs to reinstate pensions that the union agreed to get rid of for newer staff after the monetary disaster, improved retiree advantages and shorter work hours. The union additionally needs to get rid of a wage system that begins new hires at a lot decrease wages than the highest U.A.W. pay of $32 an hour.

As of Friday final week, the businesses had supplied to boost pay by round 14.5 p.c to twenty p.c over 4 years. Their gives embrace lump-sum funds to assist offset the consequences of inflation, and coverage adjustments that might carry the pay of latest hires and short-term staff, who sometimes earn a few third lower than veteran union members.

In a last-minute try to hold meeting strains working, G.M. supplied its staff a 20 p.c elevate late Thursday and mentioned it was keen to pay cost-of-living changes to veteran staff. The 20 p.c enhance can be way over staff had acquired in many years. However the union rejected the provide, which it says would barely compensate for inflation.

Leaders of the automakers have criticized the U.A.W.’s ways, specializing in Mr. Fain, who grew to become president in March and declared an finish to what he mentioned have been overly pleasant relations between union leaders and auto executives. He took workplace after a federal corruption investigation resulted in jail phrases for 2 former U.A.W. presidents.

Carlos Tavares, the chief government of Stellantis, has referred to as Mr. Fain’s technique “posturing.” Mr. Farley of Ford mentioned the 2 sides must be negotiating as a substitute of “planning strikes and P.R. occasions.” And Mary T. Barra, the G.M. chief government, mentioned that “each negotiation takes on the persona of its chief.”

If the autoworkers are profitable, they may encourage staff in different industries. Union activism is on the rise: Hollywood screenwriters and actors have been on strike for months, and in August, United Parcel Service staff received their largest raises ever in a contract negotiated by the Worldwide Brotherhood of Teamsters.

“Employees have been squeezed for too lengthy and now are realizing they’ll do one thing about it,” mentioned Mijin Cha, an assistant professor on the College of California, Santa Cruz, who research the connection between labor’s pursuits and the struggle in opposition to local weather change. “Folks see there’s a pathway to extra financial safety and staff do have energy collectively.”

Late on Friday, at an outside rally in downtown Detroit attended by a number of hundred U.A.W. members, Mr. Fain launched Senator Bernie Sanders, a Vermont impartial, who advised the gang: “The struggle you might be waging right here is not only about first rate wages and dealing situations and pensions within the auto trade. It’s a struggle to tackle company greed.”

The strikes come as auto manufacturing remains to be recovering from the consequences of the pandemic, which brought on shortages of semiconductors and different parts. Automobile costs and wait occasions have come down, however supplier inventories stay low and a prolonged strike might finally make it arduous to seek out well-liked U.S.-made fashions.

“We’re not again to hurry inventory-wise,” mentioned Wes Lutz, the proprietor of Excessive Dodge, a automotive dealership in Jackson, Mich.

Shortage shouldn’t be all the time unhealthy for carmakers. It allowed them to earn larger revenue margins through the pandemic. And it might profit any carmakers that have been having hassle shifting some fashions. Pat Ryan, chief government of the car-shopping app Co-Pilot, mentioned that Stellantis had not less than 100 days of stock for manufacturers like Dodge and Chrysler, and {that a} strike might assist it clear many sellers’ heaps.

Nonetheless, if costs for well-liked fashions rise, that will probably be yet one more pace bump within the Federal Reserve’s highway to decreasing inflation, and a political legal responsibility for Mr. Biden. The president, who has no formal position within the negotiations, mentioned Friday that he had been in contact with union leaders and auto executives, along with dispatching the 2 administration officers to Detroit.

Reporting was contributed by Neal E. Boudette, J. Edward Moreno, Santul Nerkar and Jeanna Smialek.