WASHINGTON (Reuters) -U.S. President Donald Trump said on Thursday the United States would impose a 35% tariff on imports from Canada next month and planned to impose blanket tariffs of 15% or 20% on most other trade partners.

In a letter released on his social media platform, Trump told Canadian Prime Minister Mark Carney the new rate would go into effect on Aug. 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% tariff on copper.

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% or 15%. We'll work that out now," Trump was quoted as saying by the network.

(Reporting by Jeff Mason, Jasper Ward and Ismail Shakil; Editing by Lincoln Feast.)