Michigan and California, two US manufacturing powerhouses, acted on Thursday to allow factories to reopen from coronavirus lockdowns over the next few days, as millions more Americans joined the ranks of workers left jobless by the pandemic.

Governor Gretchen Whitmer of Michigan gave the go-ahead to manufacturers in her state to restart on May 11, removing a major obstacle to North American automakers seeking to bring thousands of idled employees back to work this month.

The US auto sector accounts for 6 per cent of US economic output, with more than 835,000 Americans employed in vehicle manufacturing.

Whitmer, however, extended her stay-at-home order for two more weeks to avoid a new wave of coronavirus infections in an industrial Midwestern state hard hit by the virus and by business closures.

Whitmer had held off easing the state’s lockdown, drawing protests and hampering efforts to restart vehicle assembly anywhere in the United States because key parts suppliers are based in and around Michigan’s automaking hub of Detroit.

“We’re not out of the woods yet, but this is an important step forward,” the governor, a first-term Democrat, said in a statement.

Mexico is another link in the chain. If it does not allow suppliers to restart, automakers will not be able to resume most US production for more than a few days, auto executives said.

The Mexican government aims to inform the public on Monday of its plans to reopen the auto industry, a senior official said.