Canadian Prime Minister Mark Carney has considered the remote possibility of US military action against Canada, according to an interview with The New York Times.

Carney told the Times that his administration has carefully examined the "extreme tail risk" scenario where the US takes military action against his country, and had prepared accordingly, without providing further detail.

"I think you have a responsibility in these roles to look at extreme tail risk," Carney told the Times. "That's just risk management. That's not a base case, but it would be irresponsible not to" prepare.

Tensions between the neighbouring countries have flared under US President Donald Trump.

Any conflict would likely be highly imbalanced. The US military has more than 2 million active-duty and reserve troops, while Canada has fewer than 200,000, according to their governments. Similarly, as of 2024, the US possessed 65 military submarines, compared to Canada's four.

Canada, though, has the longest coastline in the world and is close to the Arctic, two circumstances that have prompted Carney to boost defence spending since he took office.

Meanwhile, Trump has frequently talked about Canada as the "51st state". He also started a trade war with it that deepened last month as the two countries began exchanging tit-for-tat tariffs on a number of products.

Even since then, Carney told the Times, he speaks with Trump "frequently".

"From my perspective, we have a good relationship in the sense of we can pick up the phone and talk to each other about issues," he told the outlet.

"He's direct. I'm direct in terms of where positions are. It's much more efficient that way, and so you know that exists and that will continue to exist."

Carney said he believed there was still a path to resume trade negotiations with the US. Returning to their amicable ties would be beneficial for both countries, he said.