US President Joe Biden has called for a tripling of tariffs on some steel and aluminum from China.
It is the latest protectionist policy adopted by Mr Biden as he campaigns for re-election against Donald Trump, known for his tough trade stance against China.
The White House said the plan was aimed at protecting American jobs against « unfair » competition.
China has previously denied allegations of dumping steel and aluminum overseas.
Dumping is the sale of excess product to another country at a very cheap price and often destroys the local industry's own market for that product.
Speaking to members of the United Steelworkers union in Pennsylvania on Wednesday, the president said Chinese prices are « unreasonably low » because the government is subsidizing them so they « don't have to worry about making a profit. »
« They are cheating, » Mr Biden said. « We've seen the damage in America. »
He said tens of thousands of steelworkers lost their jobs in the early 2000s due to Chinese imports.
He said that we will not let this happen again.
The Chinese embassy in the US said it « strongly opposes » Mr Biden's proposed measures.
« Many of the US's trading partners, including China, are deeply dissatisfied with the US's frequent use of the US to impose restrictions and politicize trade issues on the grounds of national security, non-market behavior, overcapacity and other reasons, » embassy spokesman Liu Pengyu said. A statement to the BBC.
Mr Pengyu said he hoped the US would work with China to « stop activities that violate international economic and trade rules » and repeal the tariffs.
The International Monetary Fund warned on Tuesday that this kind of geopolitical tension could damage global economic growth and push inflation in the wrong direction.
The White House has denied the tariffs – which would raise a key border tax rate from an average of 7.5% to 25% on small imports – would raise prices in the US.
Mr Biden discussed the plan – and other pro-manufacturing initiatives – at a campaign rally in Pittsburgh, a major base for the US steel industry.
He and Mr Trump are vying for the support of working-class voters, who are likely to be a key constituency in the November election.
The White House said it would investigate unfair trade practices in the Chinese shipbuilding and logistics industries at the request of the American Steelworkers Union and others.
The White House said it would press for action against Chinese companies that evade US border taxes by shipping through Mexico.
Mr Biden has also spoken out against the takeover of Japan's Nippon Steel by US Steel, saying he believes the business should be US-owned.
The higher tariffs will affect metal imports that are being reviewed under a so-called 301 investigation, which focuses on policies that affect U.S. trade.
Many steel and aluminum imports from China already face border tariffs, including a 25% tariff on some steel products, which the US imposed under former President Donald Trump using national security justifications.
They were said by the World Trade Organization to be in violation of global trade rules and were subsequently dialed back to several countries.
Those tariffs marked a major shift in Washington's approach to trade, which had long been dominated by a free-market, pro-trade consensus.
Mr Trump, who has called himself a « tax man », has vowed to be more aggressive on trade if re-elected.
He has proposed a 10% border tax on all imports, up from 60% on goods from China.