Trump had announced -- then halted -- sweeping 25 percent levies on Canadian and Mexican imports this month over illegal immigration and deadly fentanyl, with Canadian energy to face a lower rate.

But the month-long pause ends next Tuesday.

Following reporters' questions on whether he planned to proceed on the tariffs next week, Trump wrote on social media Thursday that until the problem of fentanyl stops "or is seriously limited," the proposed levies will happen as scheduled.

"China will likewise be charged an additional 10 percent Tariff on that date," he added, referring to March 4.

Earlier this month, Trump already imposed a sweeping 10 percent tariff hike on imports from China, prompting Beijing to retaliate.

A US official confirmed to AFP that the new 10 percent levy adds to the existing one over fentanyl, saying that there has been "insufficient progress" on the drug front.

The official added that Washington had to act against all three countries in order to tackle the fentanyl issue.

On Thursday, Chinese Commerce Minister Wang Wentao expressed concerns over Washington's earlier 10 percent tariff.

"China firmly opposes this and has taken corresponding countermeasures, which was a necessary move to safeguard its own legitimate rights and interests," Wang said in a letter to newly confirmed US Trade Representative (USTR) Jamieson Greer.

Mexican President Claudia Sheinbaum on Thursday said she hoped to speak with Trump to avoid being hit by his threatened tariffs.

A high-level Mexican delegation is in Washington in search of an agreement.

And the head of a Canadian business council warned Wednesday that Trump's threats on Canadian imports have fundamentally altered trade ties between the neighbors -- so much so that a North American free trade pact could be doomed.

- Reciprocal tariffs -

Besides levies over fentanyl, Trump added on Truth Social that an April 2 date for so-called reciprocal tariffs "will remain in full force and effect."

These will be tailored to each US trading partner, with details to come after government agencies complete studies that Trump has called for on trade issues.

"How you treat us is how you get treated," said Commerce Secretary Howard Lutnick in a Fox News interview Wednesday about the reciprocal levies.

In his letter to Geer, Wang noted that Trump has called for many trade investigations "aimed at China" and called for both sides to resolve their differences via dialogue.

Beijing has pushed back against US fentanyl concerns, saying Washington had to solve the issue itself rather than taking aim at other countries with levies.

Rather than the drugs being supplied directly to the United States, a Congressional Research Service report noted last year that US-bound fentanyl appears to be made in Mexico using chemical precursors from China.

While some precursors face international controls, others may be made and exported legally from countries like China.

In early February, China's foreign ministry additionally warned that fresh tariffs could hurt counternarcotics cooperation between both sides.