Speaking at the U.S. Steelworkers headquarters in Pittsburgh Wednesday, President Joe Biden said he'd ask the U.S. trade representative to consider tripling of tariffs on Chinese steel and aluminum imports and other protections for the U.S. steel and aluminum industry. 

The Pennsylvania-born president, noting the importance of the swing state in the November elections, said Wednesday it was Pittsburgh and union workers who elected him before, and he'll return the favor. The president told supporters in the crowd that, "You've had my back and I promise I have your back." 

"The backbone of America has a steel spine," Mr. Biden said. "It really does have a steel spine. You've heard me say it before — Wall Street didn't build America; the middle class built America, and you guys built the middle class — unions built it. And that's why I'm here today: to announce a series of actions that (show) I stand by you, the American steelworker." 

Mr. Biden said he would urge the U.S. trade representative, Katherine Tai, to triple Chinese steel and aluminum tariffs from their current rate of 7.5% if the USTR finds during an ongoing investigation that the Chinese are exercising anti-competitive trade practices in the steel and aluminum industry. The White House believes American workers face "unfair competition" from Chinese imports, and high-quality U.S. products are undercut by "artificially-low priced" Chinese alternatives that use higher emissions, according to a White House fact sheet. 

The president said China is also sending steel and aluminum through Mexico first in order to avoid U.S. tariffs, which the U.S. will be working with Mexico to prevent. Tai is also launching an investigation into China's practices in the maritime, shipbuilding and logistics sectors, the White House says. 

Mr. Biden took opportunities during his speech Wednesday to blast former President Donald Trump, whom the president referred to only as "my predecessor." Without mentioning the former president's ongoing criminal trial in New York, Mr. Biden noted that his predecessor is "busy," eliciting laughs from the audience. 

"Taken together, these are strategic and targeted actions that are going to protect American workers and ensure fair competition," Mr. Biden said Wednesday. "Meanwhile, my predecessor and the MAGA Republicans want across-the-board tariffs on all imports from all countries that could badly hurt American consumers."

The president later told reporters he's not concerned the potential tariffs could affect his relationship with Chinese President Xi Jinping. 

The steel and aluminum announcement comes amid the planned sale of U.S. Steel to the Japanese-owned Nippon Steel, which the president strongly opposes. U.S. Steel should remain an American company, Mr. Biden said Wednesday, and "that's going to happen, I promise you." 

• U.S. is pushing China to change a policy threatening American jobs, Treasury Secretary Yellen says

As the president continues his three-day swing through Scranton, Pittsburgh and Philadelphia, his campaign is launching a six-figure, five-day ad blitz highlighting Mr. Biden's pro-labor stances. Pennsylvania is a battleground state this November, with Trump and Mr. Biden neck-and-neck in national polls. 

"Scranton values or Mar-a-Lago values," Mr. Biden said during a speech in Scranton Tuesday, referencing Trump's luxurious Florida resort. "These are the competing visions for our economy, and they raise questions of fundamental fairness at the heart of his campaign." 

Bo Erickson contributed to this report 

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Kathryn Watson

Kathryn Watson is a politics reporter for CBS News Digital based in Washington, D.C.