The intensity of a historic strike by auto workers in the U.S. has entered its eighth day after two major groups were called to join the action, amid fears it could disrupt production, disrupt supply chains and hurt Americans. Economic development.

On Friday, Sean Fine, president of the United Auto Workers union, called on parts distribution centers of General Motors and Stellandis to stop work until Friday afternoon at 38 distribution centers in 20 US states.

Last week, the United Auto Workers union began an unprecedented simultaneous strike at an assembly plant for General Motors, Ford and Stellar, but analysts expect an expansion of the strikes to include factories that make more profitable trucks like Ford’s F-150 and Chevrolet Silverado. GM and Ram from Stellandis.

Fine explained that the three factories that have been on strike since September 15, when collective agreements expire without agreement on new contracts, will continue their operations.

About 12,700 workers went on strike at factories in Missouri, Michigan and Ohio that produce the Ford Bronco, Jeep Wrangler, Chevrolet Colorado and other popular models.

The union leader warned that more of the 146,000 union members working at the three companies in Detroit will join if new contracts are not reached before 1600 GMT on Friday.

The union’s president announced an extension of the strike at General Motors and Stellandis teams, citing a lack of progress in negotiations that had made “real progress” with Ford. He confirmed that a “breach” had been made, but that “serious problems” remained.

The union is demanding a 40 percent pay rise over four years, which is equivalent to what the leaders of these groups have received in the past four years. All three companies proposed a 20 percent wage hike over four-and-a-half years.

The union called on US President Joe Biden, who has supported the strikers on several occasions, to join the action.

Biden advocated “fair sharing of record profits.” On Wednesday he said he was “proud” that his administration was described as “the most pro-union administration in American history.”

The union is also demanding scrapping of the tiered pay structure, which it says has created a huge gap between new and old employees.

Standard & Poor’s said the strikes, which began on Sept. 15 and will continue for several weeks, could reduce U.S. third-quarter gross domestic product by 0.39 percent and cause “disruptions” to global auto supply chains.

Earlier, all three companies confirmed that they were preparing contingency plans to face further strike action in the US.