President Joe Biden has joined members of the United Auto Workers union on the picket line in Michigan, a first for a sitting US president.
Flanked by union workers and holding a red megaphone, Mr. Biden said a few words to the assembled crowd.
The UAW declared a strike in November targeting Ford, General Motors and Stellantis, pushing the three major car companies for higher pay and other improvements in new labour contracts.
Biden's visit to local car workers comes a day before his main electoral rival, Donald Trump, does the same.
The White House said the president will not get into negotiations.