President Joe Biden is calling on the U.S. Trade Representative to triple the China tariff rate on steel and aluminum imports as he makes the rounds in the key battleground state of Pennsylvania.

On Wednesday, the president will visit the United Steelworkers headquarters in Pittsburgh.

Biden’s demand to raise the current 7.5% average tariff on steel and aluminum is an effort to make clear that his administration’s recent warnings about China’s trade practices are not empty threats.

On a visit to China last week, Treasury Secretary Janet Yellen raised concern that Chinese subsidies were creating an oversupply of clean energy products, like solar panels and electric vehicles, that would outpace domestic demand. She worried that overcapacity could be dumped on global markets at artificially cheaper prices, potentially stifling competition.