US President Donald Trump has said he is immediately ending all trade negotiations with Canada.

In a post on Truth Social, Trump wrote that the country had run an advert featuring former US President Ronald Reagan speaking negatively about tariffs.

Based on their egregious behavior, ALL TRADE NEGOTIATIONS WITH CANADA ARE HEREBY TERMINATED, Trump wrote late on Thursday.

The US president has imposed a 35% levy on Canadian imports, although he has allowed exemptions for goods that fall under the USMCA - a free trade agreement with Mexico and Canada that Trump negotiated during his first term.

Trump said the video, sponsored by the Ontario government, was designed to interfere with the US Supreme Court, referring to an upcoming decision in November on whether Washington's sweeping global tariffs are legal.

The court's decision represents the biggest test of Trump's presidential authority and signature economic policy, potentially forcing the US to refund billions collected in tariffs.

In the minute-long advert published last week, Reagan's voice is heard narrating over images that include the New York Stock Exchange and cranes adorned with both US and Canadian flags.

The video excerpts a 1987 national radio address by Reagan that focused on foreign trade.

When someone says 'let's impose tariffs on foreign imports', it looks like they're doing the patriotic thing by protecting American products and jobs. And sometimes, for a short while it works, but only for a short time, Reagan says.

His address highlights that high tariffs inevitably lead to retaliation by foreign countries and the triggering of fierce trade wars, causing markets to shrink and businesses to shut down.

In response, the Ronald Reagan Foundation stated that the Ontario government had used selective audio and video of the former US president's remarks without permission. The foundation is currently reviewing its legal options.

Ontario Premier Doug Ford, who has been a vocal critic of Trump's economic policies, expressed his determination against American tariffs. His government launched a $75 million CAD advertising campaign against US tariffs.

The situation escalates as Trump has implemented sector-specific levies on Canadian goods, intensifying the strain between the two nations.