President Donald Trump said Monday that 25% tariffs on imports from Mexico and Canada will start Tuesday, sparking renewed fears of a North American trade war.

“Tomorrow — tariffs 25% on Canada and 25% on Mexico. And that’ll start,” Trump told reporters in the Roosevelt Room.

Trump has said the tariffs are to force the two U.S. neighbors to step up their fight against fentanyl trafficking into the U.S.

Trump provided a one-month delay in February as both countries promised concessions. But Trump said Monday that there was “no room left for Mexico or for Canada” to avoid the steep new tariffs.

U.S. stock markets moved sharply lower after Trump’s comments.

Trump said he would also add on another 10% tariff on goods from China, on top of the initial 10% he put in place last month.