JEDDAH, Saudi Arabia, March 12, 2025 (BSS/AFP) - US Secretary of State Marco Rubio headed Wednesday to Canada on the highest-level visit by the administration of President Donald Trump, who has unleashed a trade war described by the United States' neighbour as an existential challenge.

Rubio is attending Group of Seven talks of foreign ministers in Charlevoix, Quebec, where he plans to press the club of industrial democracies -- unified in backing Ukraine after Russia's 2022 invasion -- to support Trump's approach of pushing both Moscow and Kyiv to make concessions.

Rubio was taking an unusually circuitous route, departing early Wednesday from the Saudi port city of Jeddah, where a day earlier he met top Ukrainian officials to discuss an initial ceasefire plan.

In most US administrations, presidents and senior officials make Canada a first destination and the visits attract little attention, with the friendly neighbours focusing on reaffirming their longstanding ties.

But since returning to power Trump has taken a sledgehammer to Canada, mocking the less populous country by saying it should become the "51st state" of the United States and hitting it with tariffs.

Rubio arrives the same day that Canada, along with other US trading partners, is being hit by a blanket 25 percent levy on all steel and aluminium imports.

Trump on Tuesday threatened to double the tariff rate on Canada but backed down after Ontario, the most populous province, agreed to stand down on a surcharge on electricity to three US states.

Rubio acknowledged that he would likely discuss trade tensions when he meets Canadian Foreign Minister Melanie Joly but said the two countries still had "common interests", including in the G7.

"Our obligation is to try, to the extent possible, to not allow the things we work on together to be impacted negatively by the things we disagree on right now," Rubio told reporters on his way to Saudi Arabia.

Canada's outgoing Prime Minister Justin Trudeau warned Sunday that the country faced "an existential challenge" from its southern neighbour.

Mark Carney, who will soon succeed Trudeau, warned that "the Americans want our resources, our water, our land, our country".

The New York Times recently reported that Trudeau's sense of alarm grew when Trump told him he wants to revise a treaty dating from 1908 that sets the countries' border.

Rubio said he did not know if Trump raised the border treaty but that he did not expect the issue to come up at the G7 talks.