Thousands of employees represented by the United Auto Workers union went on strike Friday at three major US assembly plants after the two sides failed to reach a new contract.

About 13,000 combined workers from a General Motors assembly plant in Wentzville, Mo., a Ford factory in Wayne, Mich., and a Stellantis Jeep plant in Toledo, Ohio, walked off the job as the UAW presses the so-called Big Three for better wages and benefit offers for workers. 

It’s the first time in the union’s 88-year history of simultaneously striking at all three companies.

Contracts for 146,000 auto workers expired at 11:59 p.m. Thursday, but employees at all other plants will continue working — at least for the time being.

UAW President Shawn Fain warned that more walkouts could be scheduled if companies don’t move on bargaining.

As soon as the contracts expired, crowds of workers held pro-union signs and chanted “We are the union! Mighty Mighty Union! All the workers union! An ass-kicking union!” outside the plants. 

As the strike began, Fain joined workers at the gates of the Ford assembly plant which manufactures Bronco SUVs and Ranger midsize pickup trucks and employs 3,300 people who will strike. 

“Enough is enough. It’s time to decide what kind of a world we want to live in. And it’s time to decide what we are willing to do to get there,” Fain told the striking union members at Ford. 

Workers at all other plants remained on the job as their union brothers and sisters led the charge for better pay, but Fain warned that there will be more walkouts if the manufacturers do not move closer to the union’s requests. 

“They could double our raises and not raise car prices and still make millions of dollars in profits,” he said. “We’re not the problem. Corporate greed is the problem.”

The union boss said the companies can afford to pay their workers more to make up for concessions made beginning back in 2007 to help the automakers through tough times. The manufacturers have made billions in profits since then and only spend 4% to 5% of a vehicle’s cost on labor. 

UAW has asked the three companies for 36% pay raises over four years, an end to varying tiers of pay for workers, pension increases for retirees, a return to defined-benefit pensions for new hires instead of only 401(k) plans and a 32-hour work week without a pay deduction. 

Ford and GM have most recently offered 20% pay raises and Stellantis, formerly known as Fiat Chrysler, was last known to have offered 17.5% raises. 

The companies have called the union’s demands unreasonable and said UAW has not responded to their latest offers — which Ford said was “historically generous.”

“If implemented, the proposal would more than double Ford’s current UAW-related labor costs, which are already significantly higher than the labor costs of Tesla, Toyota and other foreign-owned automakers in the United States that utilize non-union-represented labor,” Ford said in a statement late Thursday.

GM manufacturing chief Gerald Johnson said the union’s initial demands would have cost more than $100 billion.

“That’s unreasonable,” he said in a video statement posted Thursday night. “It’s more than twice the value of all of General Motors and absolutely impossible to absorb and still compete in today’s automotive market.”

With Post wires