President Joe Biden forcefully sided with the striking United Auto Workers on Friday, dispatching two of his top aides to Detroit and calling for the three biggest American car companies to share their profits with employees whose wages and benefits he said have been unfairly eroded for years.

In brief remarks from the White House hours after the union began what it called a targeted strike, Biden acknowledged that the automakers had made “significant offers” during contract negotiations, but he left no doubt his intention to make good on a 2020 promise to always have the backs of unions.

“Over generations, autoworkers sacrificed so much to keep the industry alive and strong, especially the economic crisis and the pandemic,” Biden said. “Workers deserve a fair share of the benefits they helped create.”

Biden said that Julie Su, the acting secretary of labour, and Gene Sperling, a top White House economic adviser, would go to Michigan immediately to support both sides in the negotiations. But he said the automakers “should go further to ensure record corporate profits mean record contracts for the UAW”.

For decades, Biden has been an unapologetic backer of unions who rejects even the approach of some Democrats when it comes to balancing the interests of corporate America and the labour movement.

During the past several years, he has helped nurture what polls suggest is a resurgence of support for unions, as younger Americans in new-economy jobs push for the right to organise at the workplace. Biden declares that “unions built the middle class” in every speech he delivers.

“That was most pro-union statement from a White House in decades, if not longer,” Eddie Vale, a veteran Democratic strategist who worked for years at the AFL-CIO, said after the President’s remarks.

Earlier in the day — even before the President’s White House comments — Suzanne P. Clark, the head of the US chamber of commerce, issued a statement blaming the strike on Biden for “promoting unionisation at all costs”.

After Biden’s remarks, Neil Bradley, the group’s top lobbyist in Washington, said the President’s message and the pro-union policies his administration has pursued have “emboldened these demands that just aren’t grounded in reality”.