President Joe Biden wants to triple tariff rates on Chinese steel and aluminum if investigators confirm allegations of the country’s unfair trade practices.

“The backbone of America has a steel spine,” he said Wednesday during a visit to the United Steelworkers union headquarters in Pittsburgh. “It really does.”

Biden wants the U.S. Trade Representative to increase the 7.5% rate as federal regulators raise the alarm about China’s subsidized steel exports that flood the market with cheaper, lower-quality materials.

“They’re not competing, they’re cheating,” he said. “And we’ve seen the damage here in America.”

It’s the final stop on Biden’s three-day tour across Pennsylvania – his native state and a key battleground in the presidential election, where labor unions wield political influence.

“I’m proud to be the most pro-union president in American history,” Biden said. “Where I was raised, it ain’t labor, it’s unions.”

In March, the United Steelworkers praised the president for speaking out against a $14.9 billion offer from a Japanese company to buy U.S. Steel, based in Pittsburgh roughly one mile from the union’s headquarters.

“It should remain a totally American company,” Biden said. “American owned, American operated, by American union steelworkers, the best in the world. And that’s going to happen, I promise you.”