Around 4,000 United Auto Workers members at Mack Trucks will strike Monday after rejecting a tentative agreement in the latest dispute between the union and auto companies.

Some 73% of UAW workers rejected the agreement, the union said in a post on X, the social media platform formerly known as Twitter. The strike will start at 7 a.m. local time. The union’s claims include wage increases, cost-of-living allowances and healthcare coverage.

“I’m inspired to see UAW members at Mack holding out for a better deal, and ready to stand up and walk off the job to win it,” UAW President Shawn Fain said in the post.

The strike action against Mack Trucks, owned by Sweden’s Volvo AB, opens a new front in the UAW’s fight for better pay and conditions. Last month it launched an unprecedented strike against the Big Three Detroit automakers — General Motors Co., Ford Motor Co. and Stellantis NV as Fain pushed for 40% pay increases over the next four years and a 32-hour work week.

Fain on the weekend won a landmark concession from GM to bring battery plant workers into the union’s fold, a move that will pressure Ford and Stellantis to follow suit and secure labor’s role in the transition to electric vehicles.

Read More: UAW Skips Strike Expansion, Paves Way for EV Plant Unionization

The offer from GM, made shortly before Fain spared all three automakers from more walkouts, may shape Detroit carmakers’ labor relations for decades to come as EVs become a bigger slice of production and sales.