General Motors and the United Auto Workers union have reached a tentative contract agreement that could end a six-week-old strike against Detroit carmaker, a person briefed on the deal said.

The deal follows the pattern set with Ford last week and Jeep maker Stellantis over the weekend.

The deals will last four years and eight months and include 25% general pay raises and cost of living adjustments.

Combined they bring the wage increase to over 30% over the life of the contract.

The deal is expected to be announced early on Monday.

The contract with GM will essentially be the same as the other two carmakers but will have differences.

GM was the last company to reach a deal, and the union added a factory in Tennessee to the strike list on Saturday in an effort to turn up the pressure.

The UAW reached tentative agreement last week with Ford and it wasted no time in hitting GM where it hurts financially,

Nearly 4,000 unionised workers on Saturday walked out of GM’s largest North American plant in Spring Hill, Tennessee, hours after the deal with Stellantis was announced.

They join about 14,000 GM workers already striking at factories in Texas, Michigan and Missouri.

Spring Hill produces the engines for vehicles assembled at nine plants as far afield as Mexico, including Silverado and Sierra pickups.

It is a big money maker for GM that amplifies the company’s financial pain after workers walked off the job last week in Arlington, Texas, where full-size SUVs including the Tahoe and Suburban are produced.

Vehicles assembled at the Spring Hill plant now joining the strike include the electric Cadillac Lyriq, GMC Acadia and Cadillac crossover SUVs.

Presidents of the Ford union locals voted unanimously in Detroit on Sunday to endorse that tentative contract after UAW President Shawn Fain explained its details, the union tweeted.

As he explained the particulars to the full membership in a later livestream, Fain, along with Chuck Browning, the UAW vice president, said the deal represents a “historical inflection point” for reviving union power in an America where “we were being left behind by an economy that only works for the billionaire class”.

Strike
Sherry Barger pickets with other workers near the General Motors plant (Nicole Hester/AP)

“UAW members at Ford will receive more in straight general wage increases over the next 4 1/2 years than we have over the last 22 years combined,” MR Browning said.

Mr Fain called the deal “a turning point in the class war that has been raging in this country for the past 40 years.”

The Ford and Stellantis pacts, which would run until April 30, 2028, include 25% in general wage increases for top assembly plant workers, with 11% coming once the deal is ratified.

The Ford agreement revives cost-of-living adjustments that the UAW agreed to suspend in 2009 during the Great Recession.

At Stellantis, workers get cost-of-living pay that would bring raises to a compounded 33%, with top assembly plant workers making more than 42 US dollars per hour.

Top-scale workers there now make around 31 US dollars per hour.

Starting wages for new Stellantis hires will rise 67% including cost-of-living adjustments to over 30 US dollars per hour.

Temporary workers will get raises of more than 165%, while workers at parts centres will get an immediate 76% increase if the contract is ratified.

Like the Ford agreement, it will take just three years for new workers to get to the top of the assembly pay scale, the union said.

Similarly, the union won the right to strike over plant closures.

Bruce Baumhower, president of the local union at a large Stellantis Jeep factory in Toledo, Ohio, that had been on strike since September, said he expected workers to vote to approve the deal because of pay raises including the immediate 11% raise on ratification.

“It’s a historic agreement as far as I’m concerned.”

The UAW began targeted strikes against all three carmakers on September 15 after its contracts with the companies expired.

At the peak, about 46,000 UAW workers were on strike — about one-third of the union’s 146,000 members at all three companies.