UAW expands strike against Big 3 automakers

A labor strike against the three major U.S. automakers expanded further on Friday amid ongoing contract negotiations.

United Auto Workers President Shawn Fain called an additional 7,000 workers to the picket line, bringing the total number of striking workers to 25,000. The workers will begin striking starting at noon on Friday.

An expansion of the work stoppage draws on workers from a Ford assembly plant in Chicago and a General Motors facility in Lansing, Michigan.

"Sadly, Ford and GM have refused to make progress at the table," Fain said. "What we win at the bargaining table depends on the power we build on the job. It’s time to use that power."

The union chose to forego a further walk out at Stellantis, the parent company of Jeep and Chrysler, due to progress in ongoing talks, Fain said.

"We’re excited about this momentum at Stellantis and hope it continues," Fain said.

The UAW, which represents nearly 150,000 American autoworkers, launched a strike against General Motors, Ford and Stellantis -- often called the "Big 3" -- on Sept. 15. Almost 13,000 workers walked out of three auto plants in Michigan, Missouri and Ohio that day. The union is utilizing a "stand-up" strike method to target specific plants and add to the list if a deal isn't reached.

MORE: Biden says he will join picket line as UAW strike expands

After the unprecedented strike began, Ford laid off 600 workers who assemble cars at a plant in Michigan on Sept. 15. Workers in the paint department at a nearby plant are out on strike, leaving the assembly workers without adequate parts since the parts require paint before they can be put together into cars, a company spokesperson told ABC News.

On Sept. 22, Fain announced 38 new strike locations targeting GM and Stellantis, saying all parts distribution locations for the two companies at cities across 20 U.S. states will now join the walkouts. Ford was excluded at the time due to substantial progress at the bargaining table. Approximately 5,625 additional UAW members joined the picket line that day, bringing the overall total to more than 18,000.

It was unknown how many more targets would be picked for Friday, as the strike nears its fourth week. But it was clear that all three Detroit-based companies would be potential options if there was no progress.

Sticking points in negotiations were wage increases and the length of the workweek. The union is demanding a 46% pay increase combined over the four-year duration of a new contract, as well as a 32-hour workweek at 40-hour pay. So far, GM, Ford and Stellantis have each put forward proposals that offered workers a 20% pay increase over the life of the agreement but preserved a 40-hour workweek.

MORE: Strike against automakers could slow US economy, trigger job losses

Economists have warned that while the U.S. has yet to see any massive effects on its economy, a prolonged strike lasting a month or more could damage the country's GDP and increase the chances of heading into a recession. Economists previously told ABC News that a strike could result in billions of dollars in losses, disruption to the supply chain and other financial consequences.

On Thursday, Fain accused GM and Stellantis of enabling violence against striking workers, pointing to incidents that occurred in Michigan, Massachusetts and California. Both companies denied the allegations and cited an escalation in behavior on the picket line.

President Joe Biden has deployed acting Labor Secretary Julie Su and White House senior adviser Gene Sperling to Detroit to offer their support for the parties in reaching an agreement. Biden himself traveled to Michigan this week to join the picket line "and stand in solidarity with the men and women of UAW as they fight for a fair share of the value they helped create."

ABC News Jason Volack contributed to this report.