The United Auto Workers (UAW) union has declared a strike targeting Ford, General Motors and Stellantis, in a bid to put pressure on the carmakers to grant higher pay and make other improvements in new labour agreements.
It comes at a time of broader labour unrest and casts a cloud of uncertainty over an industry that accounts for 3% of the national economy.
US President Joe Biden has been forced to weigh in on the dispute, which is playing out in states that have disproportionate importance in national elections.
The UAW was founded in 1935 to represent workers at America’s motor giants: Ford, GM and Chrysler – now part of Stellantis.
It was a hugely powerful force in US politics after World War Two, at a time when those companies were the world’s pre-eminent car giants and manufacturing jobs in the motor industry were seen as a path to the middle class.