Mark Carney, an economist and political newcomer, has been sworn in as Canada's new prime minister and delivered a speech vowing to "never" become a part of the United States.

He takes office on Friday just days after being elected leader of the governing Liberal Party and amid an ongoing trade war with US President Donald Trump.

"We know that by building together, we can give ourselves far more than anyone else can take away," he said remarks after the ceremony.

Carney replaces outgoing Prime Minister Justin Trudeau, who was in office for nine years, after a landslide victory in last week's Liberal leadership race.

"We will never, in any shape or form, be part of the US," Carney said told reporters in Ottawa on Friday, referring to Trump's musings that Canada join the US as its "51st state".

"We are very fundamentally a different country," he said, later adding the notion is "crazy".

He declined to answer questions about the timing of Canada's next federal election - currently scheduled for October - but hinted he would move quickly to seek "as strong a mandate that is needed for the time".

In his first order as prime minister, Carney moved to end a policy that had been frequent attacked against by political opponents.

He ended the consumer carbon pricing programme - a key environmental policy under Trudeau that had become deeply unpopular in recent years amid high inflation.

Conservatives have criticised the tax, saying it raised the price of goods and energy for Canadian families.

At an afternoon cabinet meeting, Carney said his government will still take steps to fight climate change. An industrial carbon tax on large emitters remains in place.

Canadians receive a rebate to offset the cost of carbon pricing and will get their final cheque in April.

Canadian politics in recent months have largely been overshadowed by the trade war Trump launched after taking office in January - and with a general election on the horizon, Carney is expected to pitch himself as the best equipped candidate to take on Trump.

He previously held roles as governor of the Bank of Canada, the country's central bank, and of the Bank of England, and helped both countries weather major financial disruption.

He intends to travel to the UK and France as his first foreign trip as PM next week.

Carney said he also looks forward to speaking with Trump.

"We respect the United States. We respect President Trump," he said after the swearing in ceremony.

"President Trump is has put some very important issues at the top of his agenda."

Carney has promised to uphold Canada's reciprocal tariffs on specific American goods for as long as Trump maintains 25% universal tariffs on Canadian goods not covered by the Canada-United States-Mexico Agreement (CUSMA) trade deal.

Canada is dependent on trade with the US. Economists say it risks a recession if Trump's tariffs are fully imposed.

Several of Carney's new cabinet members served under Trudeau, and in particular he kept on those who have been working directly with the Trump administration in recent months.

They including Mélanie Joly, who remains in foreign affairs; David McGuinty, who remains in public safety; Jonathan Wilkinson, staying on as energy minister; Dominic Leblanc, who has moved from finance to trade; and François-Philippe Champagne, moved from industry to finance.

When the federal election comes, Carney's main rival will be Conservative leader Pierre Poilievre.

Before the the threat of tariffs, Conservatives enjoyed a 20-point lead in some election polls. Now polls are indicating a much closer race.

Speaking after Carney on Friday, Poilievre argued that Liberals do not deserve a fourth term in office, arguing adding they have already had nine years to improve affordability and other issues in the country.

"It will be the same Liberal results," he said.

Poilievre added that if he were to be elected prime minister, he would "face off against President Trump directly, respond with counter tariffs and take back control".

When Canadians next go to the polls, the Liberals will face not only the Conservatives - who are the official opposition with 120 seats in the House of Commons - but also the Bloc Quebecois, who have 33 seats, and the New Democrats (NDP), who have 24.

Reacting to Carney's swearing in, the leader of the NDP argued that his cabinet appointments show that there is no room for progressive Liberals under his leadership.

Jagmeet Singh said that he had failed to create separate cabinet portfolios for minister of women, youth, or people with disabilities, and described Carney as someone who has made billionaires "very rich at the cost of workers".