Canada's Prime Minister Justin Trudeau speaks to donors during the Laurier Club Holiday Party at the Canadian Museum of History in Gatineau, Quebec, on December 16, 2024. Dave Chan, AFP/file

Canada's Prime Minister Justin Trudeau announced his resignation Monday, saying he would leave office as soon as his party chooses a new leader, with slumping polls and internal division taking their toll.

After more than nine years in power, Trudeau's support within the ruling Liberal party began crumbling in 2024 due to intensifying public criticism focused on the rising cost of living.

His authority was then shaken by the surprise departure last month of his finance minister and deputy prime minister Chrystia Freeland.

"I intend to resign as party leader, as prime minister, after the party selects its next leader," Trudeau told a news conference in Ottawa following a slow-rolling political crisis that saw top Liberal allies urge him to quit.

It was not immediately clear how long Trudeau, 53, would remain in office as a caretaker premier.

He said the Liberal leadership race will be "a robust, nationwide competitive process."

That means Trudeau will continue to lead Canada when incoming US president Donald Trump takes office this month and will be tasked with leading the country's initial response to the new US administration, including a possible trade war.

Trump has vowed to impose 25-percent tariffs on all Canadian imports, which could prove devastating to the Canadian economy, and Trudeau has pledged to retaliate.

The US president-elect reacted to Trudeau's quitting by again airing his unlikely proposal that Canada should merge with its southern neighbor.

"Together, what a great Nation it would be!!!" he wrote on social media.

US President Joe Biden's outgoing administration praised Trudeau as a "stalwart friend" of the United States.

White House Press Secretary Karine Jean-Pierre told reporters Washington would "stand with" Canada and its people as they pick a new leader.

HAD YOUTHFUL ENERGY 

Before taking over the Liberal party in 2013, Trudeau was not a leading political figure.

His most prominent political attribute at the time was arguably the fact that his father, Pierre Elliott Trudeau, had been one of Canada's most famous prime ministers.

But Trudeau's youthful energy and fluency on issues that increasingly mattered to Canadians, including climate change, helped him oust Conservative prime minister Stephen Harper in 2015 elections.

Across the country, Trudeau's resignation did not surprise.

"He should have resigned over a year ago," said Toronto resident Rob Gwett, 29, adding that today's announcement was "better late than never."

Trudeau's Liberals are trailing badly in the polls to the opposition Conservatives.

He conceded Monday that he was not the best candidate to lead the party into an election that must be held this year.

"This country deserves a real choice in the next election, and it has become clear to me that if I'm having to fight internal battles, I cannot be the best option in that election," he said.

Canadian media have tipped Freeland as a possible Liberal leader, along with the former Bank of England governor Mark Carney, a Canadian who also led the Bank of Canada.

Several others are expected to join the race which could take multiple months. Liberal party president Sachit Mehra confirmed the contest will kick off this week.

ACCUSED OF GIMMICKS

In her scathing resignation letter, Freeland had accused Trudeau of focusing on political gimmicks to appease voters, including a costly Christmas tax holiday, instead of steadying Canada's finances ahead of Trump's promised tariffs.

Freeland offered a muted response to Trudeau's impending departure, thanking him for his "years of service to Canada and Canadians," in a post on X.

Whoever takes over, Andre Lamoureux of the University of Quebec in Montreal (UQAM) said they are unlikely to manage to build fresh enthusiasm around the party.

"It's a lost cause," he said.

Conservative party leader Pierre Poilievre indicated he was ready to take on whoever the Liberals put forward, dismissing all contenders for having "supported EVERYTHING Trudeau did for 9 years," in a post on X.

Trudeau's minority government had been propped up by a deal with the left-wing New Democratic Party but in December the NDP said they would vote to topple Trudeau at the next opportunity.

Trudeau has received permission from Canada's governor general to suspend all parliamentary business until March 24.

That could give the Liberals time to choose a new leader while restricting the opposition's chances to bring a vote of no-confidence.