WASHINGTON: US President Donald Trump said Monday that he would double tariffs on Canadian vehicles beginning next year, as the historically friendly neighbours spiral towards an escalating trade war.

Trump's latest threat comes after the North American neighbours failed Friday to reach a deal to avert new 50-per cent US tariffs on select Canadian goods. The duties took effect on Saturday.

"On January First, 2027, Tariffs on all Cars, Trucks, both large and small, Automotive Parts, and Steel, will be increased to 50 per cent," Trump wrote on his Truth Social platform.

The current US tariff impacting Canadian autos stands at 25 per cent for non-US content, while imported steel to the United States generally faces a 50-per cent duty.

US automakers did not immediately comment on the matter.

After walking away from what he called a "bad deal," Canadian Prime Minister Mark Carney announced retaliatory tariffs effective Sep 8.

The tariffs will target US steel and dairy, while also covering sectors like agricultural equipment, pulp and paper, as well as electronics.

On Monday, Carney said the goal of trade talks with Washington "has always been to get the best deal for Canadians, never a deal at any price or on any time frame."

He added that despite progress towards a pact, "that momentum reversed" in the end, stressing that building domestically and diversifying trade abroad has been "plan A from the start."

Over the weekend, Carney said one reason the deal collapsed was that US negotiators sought last-minute restrictions on Canadian trade deals with other countries.

US negotiators also made unacceptable "threats" to the French language and "Quebec culture," he said, referring to the French-speaking province in eastern Canada.

The United States is by far Canada's biggest trading partner, with Canadian exports to its neighbor representing 70 per cent of its overall total.

Canada is the United States' second biggest trading partner in goods this year, behind Mexico, government data showed.