United Auto Workers said on Friday the union will expand its strike against major automakers by walking out of 38 General Motors and Stellantis plants in 20 states.
Ford was spared additional strikes because the company has met some of the union's demands during negotiations over the past week, said UAW President Shawn Fain.
The union is pointing to the companies' huge recent profits as it seeks wage increases of 36 per cent over four years.
The companies have offered a little over half that amount. The UAW has other demands, including a 32-hour work week for 40 hours of pay and a restoration of traditional pension plans for newer workers.
The companies say they can't afford to meet the union's demands because they need to invest profits in a costly transition from gas-powered cars to electric vehicles.
The UAW's contract with the automakers expired at midnight on September 14, and workers walked out of a Ford assembly plant near Detroit, a GM factory in Wentzville, Missouri, and a Jeep plant run by Stellantis in Toledo, Ohio.
The initial strike has involved about 13,000 of the union's 146,000 members.
Fain said earlier this week he would call on workers at more plants to strike unless there was significant progress in contract negotiations with the carmakers. Bargaining continued Thursday, although neither side reported any breakthroughs, and they remained far apart on wage increases.
The strike until Friday had involved fewer than 13,000 of the union's 146,000 members.