DETROIT >> The United Auto Workers union said today it will not expand its strikes against Detroit’s three automakers after General Motors made a breakthrough concession on unionizing electric vehicle battery plants.

Union President Shawn Fain told workers in a video appearance that additional plants could be added to the strikes later.

The announcement of the pause in expanding the strikes came shortly after GM agreed to bring electric vehicle battery plants into the UAW’s national contract, essentially assuring that they will be unionized.

Fain said GM’s move will change the future of the union and the auto industry.

He said GM made the change after the union threatened to strike at a plant in Arlington, Texas, that makes highly profitable large SUVs.

“Today, under the threat of a major financial hit, they leapfrogged the pack in terms of a just transition” from combustion engines to electric vehicles, he said. “Our strike is working, but we’re not there yet.”

In addition to large general pay raises, cost of living pay, restoration of pensions for new hires and other items, the union wanted to represent 10 battery factories proposed by the companies.

The companies have said the plants, mostly joint ventures with South Korean battery makers, had to be bargained separately.

Today’s change means the the four U.S. GM battery plants would now be covered under the union’s master agreement and GM would bargain with the union’ “which I think is a monumental development,” said Marick Masters, a business professor at Wayne State University in Detroit.

He said the details of GM’s offer, made in writing, will have to be scrutinized.

“GM went far beyond and gave them this,” Masters said. “And I think GM is thinking they may get something in return for this on the economic items.”