More than 7,000 workers are set to walk off the job at Ford and General Motors factories, according to union boss Shawn Fain.

He said the latest action did not target Stellantis, reflecting new momentum in those discussions.

The US economy has been hit by a dispute involving roughly 18,000 workers.

US President Joe Biden and former President Donald Trump visited the Detroit area this week amid simmering labour tensions.

As part of the union’s demands, it is seeking a 40% pay raise over four years, an end to practices that give newer hires lower pay and fewer benefits, among other things.

In their view, the union’s requests would hinder their long-term investment plans. In response, they have offered a 20% pay increase as well as some other concessions.

Many workers in Michigan said they were prepared for a long strike this week.

The middle class is needed, said Emily Yettaw, who has worked at GM for 17 years. Since labour contracts expired on 14 September, the union, which represents 146,000 workers at the three companies, has gradually ratcheted up pressure on the companies to strike a deal.

Work stoppages have expanded to a Ford factory in Chicago that manufactures Explorers, as well as a GM factory in Michigan that produces large crossover SUVs like the Chevrolet Traverse and Buick Enclave.

Prior targets included 38 facilities that distribute parts to dealers and three factories at each company.