Trump says he will announce reciprocal tariffs on Tuesday or Wednesday, and they will go into effect almost immediately

President Donald Trump announced plans to impose a 25% import tax on all steel and aluminum entering the U.S., a decision expected to hit Canada the hardest.

Trump added that he would unveil details later in the week about reciprocal tariffs on countries that tax U.S. imports. However, he did not specify which nations would be targeted or whether any exemptions would be granted.

"If they charge us, we charge them," Trump told reporters while traveling from his Mar-a-Lago resort in Florida to the Super Bowl in New Orleans on Sunday.

Canada and Mexico are among the U.S.'s largest steel trading partners, with Canada being the biggest supplier of aluminum to the U.S.

During his first term, Trump imposed tariffs of 25% on steel imports and 10% on aluminum imports from Canada, Mexico, and the European Union. While the U.S. later reached an agreement with Canada and Mexico to lift those tariffs, the duties on EU imports remained in place until 2021.

Speaking aboard Air Force One on Monday, Trump confirmed his plans to reintroduce tariffs. "Any steel coming into the United States is going to have a 25% tariff," he said. "We’ll announce tariffs on everybody."

In response, Ontario Premier Doug Ford criticized Trump’s move, calling it “shifting goalposts and constant chaos, putting our economy at risk” in an online post. Ontario is home to a significant portion of Canada’s steel production.

Trump’s announcement also rattled markets in South Korea, a major steel exporter to the U.S. Shares of POSCO Holdings, a leading steel company, fell as much as 3.6%, while Hyundai Steel dropped 2.9%. Kia Corp, a major carmaker, also saw its stock decline by 3.6% during early morning trading.

This latest move marks another escalation in Trump’s aggressive trade policy, which has already provoked retaliation from China.