Starting Wednesday, importers bringing steel and aluminum goods from Mexico must prove that the metals were forged in North America or face national security tariffs, as part of the Biden administration's strategy to counter Chinese goods rerouted through Mexico to avoid duties.

Administration officials announced that importers will now be required to certify to U.S. Customs and Border Protection that the steel in their products was melted and poured in North America. Failing to do so will result in a 25% levy on global steel imports under Section 232 of the Trade Expansion Act of 1962.

Aluminum importers must certify that their products were not smelted and cast using primary aluminum from Russia, China, Belarus, or Iran, or face a 10% duty under the Section 232 program. Mexico will also require steel and aluminum importers to provide additional country-of-origin information, according to the White House.

"These actions fix a major loophole that the previous administration failed to address, and that countries like China use to avoid U.S. tariffs by shipping their products through Mexico," National Economic Advisor Lael Brainard said on a Tuesday call with reporters ahead of the announcement.

Approximately 3.8 million tons of steel entered the U.S. from Mexico in 2023. While 87% of that was melted and poured in the U.S., Mexico, or Canada, the remaining 13% originated overseas. Levies are deemed necessary to cover Beijing's steel production outside its borders, an official said.

"The Chinese ship steel from all over the world," the official told reporters. "There are Chinese companies operating elsewhere, so it is coming in from a number of countries, not just China."

Trade volumes for aluminum are much smaller, with just 6% of the 105,000 tons of aluminum entering the U.S. from Mexico last year smelted and cast outside North America, according to the White House.

The White House also announced in May that the maximum duties on Chinese steel and aluminum products imposed in response to unfair trade practices will increase from 7.5% to 25% by Aug. 1.

China, which exported over $70 billion worth of steel last year, has continued producing more steel than it can use domestically through highly polluting processes despite U.S. calls to rein in its excess capacity, officials said.

"We've been very clear with China, publicly and privately, about the sectors of concern and the trade practices that we consider unfair that are also of concern, and the fact that we are going to take actions to protect our market from those unfair practices," said another official.