Shawn Fain, the United Auto Workers president, criticized Donald Trump on Monday but declined to back Joe Biden as he reaffirmed plans to lead a general strike in the US in 2028.

Speaking to union members at the UAW national political conference in Washington DC, Fain said it was time for union members to come together.

“We have to pay for our sins of the past. Back in 1980 when Reagan at the time fired patco workers, everybody in this country should have stood up and walked the hell out,” Fain said. “We missed the opportunity then, but we’re not going to miss it in 2028. That’s the plan. We want a general strike. We want everybody walking out just like they do in other countries.”

A general strike is a mass strike across various industries around similar demands or bargaining positions. In the US, they have been virtually non-existent in recent decades given the passage of the Taft-Hartley Act in 1947 that restricted secondary strikes and the decline of labor unions in the US since the 1970s.

After successfully taking on the US auto companies, Fain has emerged as a potent political figure, courted by Trump and Biden.

Fain also used his speech to criticize Trump, telling reporters that Trump “is as a person … pretty much contrary to everything we stand for”.

But the UAW has yet to formally endorse Biden, who was the first president to walk on a picket line with striking workers in September 2023. Fain told reporters the union will be holding formal discussions on an endorsement amid rumors that Biden may address the union in person later this week.