Canada elects a new government on Monday to confront annexation threats from the United States and deal directly with US President Donald Trump, whose trade war has defined the campaign.

The Liberal Party, led by new Prime Minister Mark Carney, had looked set to lose easily to the Conservatives' Pierre Poilievre until the US president's attacks on the country sparked a sudden reversal in poll forecasts.

Carney, 60, has never held elected office and only replaced Justin Trudeau as prime minister last month. He had a lucrative career as an investment banker before serving as the central bank governor in both Canada and Britain.

Carney has argued his global financial experience has prepared him to guide Canada's response to Trump's tariffs.

He has also promised to revitalise internal trade and expand Canada's economic opportunities abroad to cut reliance on the United States, a country Carney says "we can no longer trust".

The United States under Trump "wants to break us, so they can own us", he has warned repeatedly through the campaign.

"We don't need chaos, we need calm. We don't need anger, we need an adult," Carney said in the campaign's closing days.

Poilievre, a 45-year-old career politician, has tried to keep the focus on domestic concerns that made Trudeau deeply unpopular toward the end of his decade in power, especially soaring living costs.

The Tory leader has argued Carney would bring a continuation of what he calls "the lost Liberal decade", arguing that only a new Conservative government can take action against crime, housing shortages and other non-Trump issues Canadians rank as priorities.

"You cannot handle another four years of this," he said over the weekend.

Poilievre has critiqued Trump, but insisted ten years of poor Liberal governance had left Canada vulnerable to a newly hostile United States.

Final polls indicate a tight race but put Carney as the favourite. (AFP)