WASHINGTON

US President Joe Biden and Vice President Kamala Harris pledged Monday to support union workers.

"Kamala believes as I do that unions are the spine of this economy. She will be a historic, pro-union president," Biden said at his first joint campaign event with Harris in Pittsburgh, Pennsylvania.

Marking Labor Day, he said when unions do well, all workers in America do better.

Echoing Biden, the Democratic Party's presidential nominee Harris said they are fighting to build an economy that works for all working people and that has been the vision of the labor movement.

She also expressed her opposition to the proposed sale of US Steel to Nippon Steel Corp. of Japan.

"US Steel is an historic American company, and it is vital for our nation to maintain strong American steel companies.

"And I couldn't agree more with President Biden: US Steel should remain American owned and American operated. And I will always have the back of America's steelworkers and all of America's workers," Harris said.

For the upcoming Nov. 5 presidential election, Biden said Harris is the only "rational choice."

"I trust her," he said, reiterating that selecting her as his running-mate was "the single best decision I made as president of the United States of America."​​​​​​​