WASHINGTON — The United States will levy 25% tariffs on imports of medium and heavy-duty trucks beginning Nov. 1, President Donald Trump announced in a Monday social media post.

The tariffs follow an investigation initiated in April by the U.S. Commerce Department about the national security effects of truck imports. The levies would be separate from import taxes on light-duty trucks, which have been in place for decades.

The White House did not immediately provide details on whether there would be exemptions for Mexico and Canada, where U.S. automakers have a sizable manufacturing footprint, or for countries like South Korea and Japan that recently reached trade deals with the United States.

If there are no carveouts for Mexico and Canada, General Motors Co. and Stellantis NV could face significant tariff costs. Both automakers perform final assembly for just under half of their U.S.-sold trucks in Mexico and Canada, according to data from S&P Global.

Ford Motor Co. noted that it assembles 100% of its heavy trucks at its Kentucky Truck Plant and Ohio Assembly Plant and cheered the Trump administration for the new tariffs.

"Ford applauds the Trump administration’s action on medium and heavy trucks, which supports our shared goal of growing the American auto industry and U.S. manufacturing. American autoworkers deserve a level playing field,” company spokesperson Robyn Jackson said in a statement.

GM and Toyota Motor Corp. both declined to provide a comment, as did the industry's top lobbying group, the Alliance for Automotive Innovation. Stellantis also declined to comment, though the company has previously opposed new levies.

"Stellantis does not believe that any additional measures on truck or truck parts specifically are necessary to protect national security due to the U.S.’s large existing manufacturing capacity and the small share of U.S. medium- and heavy-duty truck sales that are fulfilled by imported products," the company wrote in a public comment to the Commerce Department in May.

The U.S. market for light-duty cars and trucks is much larger than the market for heavier vehicles, but those models still play a big business role for the Detroit Three automakers.

The United States imported about $20.8 billion worth of medium and heavy-duty trucks, or roughly 246,000 finished vehicles, in 2024, according to federal data. Nearly $20 billion worth of the imports came from Mexico and Canada.

The new tariff announcement comes days after a report suggesting that Trump was on the verge of providing some light-duty tariff relief for U.S. automakers, though the White House has not shared additional details about those plans.