President Donald Trump said Monday that a steep U.S. tariff on imported heavy trucks would begin on Nov. 1, postponing the date that he initially threatened to impose such duties.

"Beginning November 1st, 2025, all Medium and Heavy Duty Trucks coming into the United States from other Countries will be Tariffed at the Rate of 25%," Trump wrote in a post on his Truth Social site.

This is a monthlong delay from the Oct. 1 start date he vowed in an earlier social media post unveiling the new duty.

The Trump administration launched a so-called Section 232 probe into imports of trucks earlier this year to determine their effects of national security, setting the stage for Trump's announcement.

Trump has used such investigations, under the authority of the Trade Expansion Act of 1962, to impose tariffs on various imported goods -- in efforts to boost U.S. manufacturing and punish countries that he says are taking advantage of his country.

Analysts, however, have noted that the impact of tariffs on heavy trucks depends on whether there are exemptions from such vehicles made in Mexico and Canada.

"The U.S. sources 78% of heavy truck imports from Mexico and 15% from Canada," said Capital Economics Economists Neil Shearing and Stephen Brown.

"A key question is whether there will be exemptions for USMCA-compliant products," they added in a note last month, referring to the U.S.-Mexico-Canada free trade agreement.

This is unclear for now, they said, flagging that product-specific tariffs -- with the exemption of auto parts -- do not necessarily contain exemptions for goods entering the United States under the North American trade pact.

"If there's no USMCA exemption, then Mexico will be most heavily affected by the large truck tariffs," they said.

Trump's sector-specific national security tariffs are seen as being on firmer legal ground than some of his other levies, which rely on emergency economic powers to target entire economies.

The latter tariffs have been challenged in court, with the Supreme Court set to hear arguments in the case next month.

All rights reserved ©2025 Agence France-Presse