Canada's Deputy Prime Minister Chrystia Freeland quit Monday in a surprise move after disagreeing with Justin Trudeau over US President-elect Donald Trump's tariff threats.

The resignation of Freeland, 56, who also stepped down as finance minister, marked the first open dissent against Prime Minister Trudeau from within his cabinet, and may threaten his hold on power.

Liberal leader Trudeau lags 20 points in polls behind his main rival, Conservative Pierre Poilievre, who has tried three times since September to topple the government and force a snap election.

"Our country today faces a grave challenge," Freeland said in her resignation letter to Trudeau, pointing to Trump's planned 25-percent tariffs on imports from Canada.

"For the past number of weeks, you and I have found ourselves at odds about the best path forward for Canada."

First elected to parliament in 2013, the former journalist joined Trudeau's cabinet two years later when the Liberals swept to power, holding key posts including trade and foreign minister, and leading free trade negotiations with the European Union and the........

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