President Donald Trump says the United States will impose a 35 per cent tariff on imports from Canada and plans to impose blanket tariffs of 15 or 20 per cent on most other trade partners.

In a letter released on Thursday on his social media platform, Trump told Canadian Prime Minister Mark Carney the new rate would go into effect on August 1 and would go up if Canada retaliated.

Trump has broadened his trade war in recent days, setting new tariffs on a number of countries, including allies Japan and South Korea, along with a 50 per cent tariff on copper.

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In an interview with NBC News published on Thursday, Trump said other trading partners that had not yet received such letters would likely face blanket tariffs.

“Not everybody has to get a letter. You know that. We’re just setting our tariffs,” Trump said in the interview.

“We’re just going to say all of the remaining countries are going to pay, whether it’s 20 per cent or 15 per cent. We’ll work that out now,” Trump was quoted as saying by the network.