President Donald Trump has said he will announce a 25% import tax on all steel and aluminium entering the US, a move that will have the biggest impact in Canada.

Trump also said that there would be an announcement later in the week about reciprocal tariffs on all countries that tax imports from the US, but he did not specify which nations would be targeted, or if there would be any exemptions.

"If they charge us, we charge them," Trump said.

He told reporters of his plans while travelling from his Mar-a-Lago resort in Florida to the Super Bowl in New Orleans on Sunday.

Canada and Mexico are two of the US's biggest steel trading partners, and Canada is the biggest supplier of aluminium metal into the US.

During his first term, Trump put tariffs of 25% on steel imports and 10% on aluminium imports from Canada, Mexico and the European Union.

But the US reached a deal a year later with Canada and Mexico to end those tariffs, although the EU import taxes remained in place until 2021.

Speaking aboard Air Force One, Trump said on Monday he would announce tariffs on "everybody" for steel and aluminium.

"Any steel coming into the United States is going to have a 25% tariff," he said.

In response, Doug Ford, the premier of the province of Ontario, accused Trump of "shifting goalposts and constant chaos, putting our economy at risk" in an online post. Canada's steel production is concentrated in Ontario.

Trump's comments also caused the stocks of major South Korean steel and car makers to fall. South Korea is a major exporter of steel to the US.

Shares of steel firm POSCO holdings dropped as much as 3.6%, while those of Hyundai Steel were down as much as 2.9%.

Those of car maker Kia Corp also fell by 3.6% during early morning trading.

Trump's move marks another major escalation in Trump's trade policy, which has already sparked retaliation from China.

Tariffs are a central part of Trump's economic vision - he sees them as a way of growing the US economy, protecting jobs and raising tax revenue.

Earlier this month, Trump threatened to impose import duties of 25% on Canadian and Mexican products but later delayed that plan for 30 days – until early March - after speaking to the leaders of both countries.

He also brought in new US levies of 10% on all Chinese goods coming into the US. Beijing has retaliated with its own set of tariffs which took effect on Monday.

Trump also said he would announce more tit-for-tat tariffs on "Tuesday or Wednesday" and that they would take effect "almost immediately" after the announcement.

"The ones that are taking advantage of the United States, we're going to have reciprocal [tariffs]," he said. "It'll be great for everybody, including other countries".

On the trip to New Orleans, Trump also signed an proclamation designating 9 February "Gulf of America" day to celebrate his order renaming of the Gulf of Mexico, as his plane crossed the body of water.

Mexico argues the US cannot legally change the Gulf's name because UN rules dictate that an individual country's sovereign territory only extends up to 12 nautical miles out from the coastline.

Trump was also asked whether he had spoken to Russian President Vladimir Putin and replied: "I don't want to talk about it, and if we are talking, I don't want to tell you about the conversations too early, but I do believe we're making progress."

"I would imagine I would be meeting with Putin at the right time… at the appropriate time," he said.

Trump also repeated his unlikely suggestions that the US could take over Canada and the Gaza Strip, saying Canada would fare better as the "51st state" and that he was "committed to buying and owning Gaza".