The United Auto Workers (UAW) union on Friday broadened its strike against General Motors and Stellantis citing a lack of progress in negotiations, although the union spared Ford from new strike activity after the two sides agreed on some provisions in their talks.

UAW President Shawn Fain said that union members will go on strike at all the parts distribution facilities for GM and Stellantis – the parent company of brands like Chrysler, Dodge, Jeep and Ram. The new strike activity covers 38 locations across 20 states in all nine of the UAW’s regions and will affect approximately 5,600 union members, which brings the number of UAW workers on strike to roughly 18,600.

"Both GM and Stellantis have rejected our profit-sharing proposals and both companies have rejected our proposals to convert temps. So today at noon Eastern time, all of the parts distribution centers at General Motors and Stellantis are being called to stand up and strike," Fain said. The union is seeking pay raises amounting to 40% over a new four-year contract in addition to expanded benefits and other provisions, while the automakers’ pay offers have been closer to 20% with an immediate 10% increase.

The UAW is running what it calls a "stand up strike" in which some of the union’s locals are asked to go on strike incrementally as the union sees fit to ratchet up the leverage on the auto companies. The union’s leaders believe that gives them flexibility in escalating the strike as needed up to a potential nationwide strike.

"Stellantis and GM in particular are going to need some serious pushing," Fain said. 

GM said it will make a statement on the broadened strike activity around noon ET, when union members are expected to walk out, and this story will be updated following the statement's release. Stellantis did not immediately respond to a request for comment.

The UAW’s broadened strike activity does not apply to any Ford facilities, as Fain cited "real progress" in negotiations with the company, but noted, "We have more work ahead of us before we can reach an agreement." Among the concessions he said the UAW has secured are the reinstatement of a cost-of-living allowance, conversion of all current temps, plus additional income security for workers in the event of a layoff that includes up to two years of healthcare.

"We continue to negotiate with the UAW and we are bargaining issue by issue - just like we did with Unifor in Canada," Ford said in a statement. 

Fain went on to call for President Biden to join the UAW workers on the picket line and said, "We invite and encourage everyone who supports our cause to join us on the picket line from our friends and families all the way up to the President of the United States."

Biden expressed support for the UAW’s strike and has considered sending administration officials to help facilitate talks without mediating, although he has not done so yet. White House press secretary Karine Jean-Pierre said Thursday that "we appreciate the fact that they are still at the negotiating table having this conversation. It is important that we result in a win-win agreement."

Temporary layoffs and work stoppages have mounted at the Big Three since the strike began last Friday. Parts shortages stemming from facilities where workers have gone on strike have had a spillover effect causing other facilities to idle as they run out of necessary parts or storage space.

FOX Business’s Philip Bodinet contributed to this report.

This is a developing story and may be updated. Please check back for updates.