The Grayson  PrestonUnited Auto Workers is gearing up to escalate its strike against the Big Three automakers today, as the union fights hard to make up for years of stagnant wages and other concessions from its members.

UAW President Shawn Fain is expected to announce at 10 a.m. ET which plants will join the group of workers who were the first to walk off the job last week, when the union's contracts with the automakers expired.

Roughly 13,000 workers at three Midwest auto plants — a General Motors assembly plant in Wentzville, Mo., a Stellantis assembly plant in Toledo, Ohio, and part of a Ford plant in Wayne, Mich. — are currently on the picket line.

"If we don't make serious progress by noon on Friday, September 22nd, more locals will be called on to stand up and join the strike," Fain announced in a video posted to Facebook Monday night, while not revealing which plants or how many would be called on next.

Fain's so-called "stand up" strike strategy is intended to keep Ford, General Motors and Stellantis on their toes with sudden, targeted strikes at strategic locations, rather than having all of the nearly 150,000 UAW auto workers walk off their jobs at once.

General Motors has temporarily laid off most of the approximately 2,000 unionized workers at its Fairfax assembly plant in Kansas as a result of the ongoing UAW strikes. The other two companies have also announced temporary layoffs at a smaller scale.

So far, the companies have failed to present wage offers that the union sees as adequate, though the automakers say they've already put generous offers on the table. The UAW is pushing for a 40% wage increase over the length of the contract.

The two sides also remain at odds over other key economic issues, including the restoration of pension and retiree health care and cost of living adjustments. The UAW says it wants to make up for concessions that propped up the automakers during the 2008 financial crisis — the effects of which workers still feel to this day.

"We haven't had a raise in years, a real raise," said Gil Ramsey, a Ford employee who's on strike in Wayne, Mich. "And everything that we gave up when the company was down on the ropes — we haven't even got that back yet."