As of last Friday, the two parties remained far apart, with the companies offering to raise pay by 14 to 16 percent over four years. Mr. Fain called that offer “insulting” and has said that the union is still seeking a 40 percent pay increase.

What role is the switch to electric cars playing in the negotiations?

The auto industry is in the middle of a sweeping transition to battery-powered vehicles, and G.M., Ford and Stellantis are spending billions of dollars to develop new models and build factories. The companies have said those investments make it harder for them to pay workers substantially higher wages. Automakers say they are already at a big competitive disadvantage compared with nonunion automakers like Tesla, which dominates the sale of electric vehicles.

The U.A.W. is worried that the companies will use the switch to electric cars to cut jobs or hire more nonunion workers. The union wants the automakers to cover workers at the battery factories in their national contracts with the U.A.W. Right now those workers are either not represented by unions or are negotiating separate contracts. But the automakers say they cannot legally agree to that request because those plants are set up as joint ventures.

What happened in the last U.A.W. strike?

The U.A.W. most recently went on strike in 2019 against General Motors. Nearly 50,000 General Motors workers walked out for 40 days. The carmaker said that strike cost it $3.6 billion.

The strike ended after the two sides reached a contract that ended a two-tier wage structure under which newer employees were paid a lot less than veteran workers. G.M. also agreed to pay workers more.