U.A.W. Says It Could Expand Auto Strikes on Friday

The United Automobile Workers union said on Wednesday that it planned to expand its strike against the big three Michigan automakers on Friday if negotiators failed to make substantial progress on new contracts.

The union ordered workers to walk off the job nearly two weeks ago at three vehicle assembly plants — each owned by one of the companies, General Motors, Ford Motor and Stellantis, the parent of Chrysler and Jeep. Last Friday the union broadened the strike to include spare parts-distribution centers owned by G.M. and Stellantis, saying it had made progress in its talks with Ford.

The U.A.W. president, Shawn Fain, is scheduled to update members in a video streamed live on Facebook on Friday morning.

The union is seeking a substantial wage increase to make up for much smaller raises over the last decade. Each of the companies has offered to lift wages by roughly 20 percent over four years, about half of what the U.A.W. is seeking. The union has demanded other measures including cost-of-living adjustments, the right to strike to protest plant closures, pensions for more workers and company-paid health care for retirees.

The three plants that have been shut down by the strike include a G.M. factory in Wentzville, Mo., a Ford plant in Wayne, Mich., and a Stellantis complex in Toledo, Ohio. They make some of the manufacturers’ most profitable models, including the GMC Canyon pickup truck, the Ford Bronco sport-utility vehicle, and the Jeep Wrangler.

The second wave of the strike idled 20 Stellantis parts-distribution centers and 18 owned by G.M. More than 18,000 U.A.W. workers are now on strike. The union represents about 150,000 workers employed by G.M., Ford and Stellantis.

The union and the companies started negotiating new collective bargaining agreements in July, but made little progress until this month. Their contracts expired on Sept. 14 and Mr. Fain called on the first round of work stoppages the following day.