King Charles III was given an enthusiastic welcome on Monday by Canadians who turned out in droves to see their monarch on his historic visit to open parliament, as part of the pushback against US President Donald Trump's annexation threats.

The 76-year-old king, who is Canada's head of state as part of the Commonwealth, was greeted at the airport by Prime Minister Mark Carney, who has invited him to give an address opening Canada's new legislature on Tuesday. 

"This historic honor matches the weight of our times," Carney said.

On their first stop in the Canadian capital, the royals visited a farmer's market, where they were cheered by thousands of Canadians. The king also dropped the puck for a street hockey game.

The so-called throne speech outlining the government's priorities is typically given by the British monarch's representative in Canada, the governor general.

Queen Elizabeth II, the king's late mother, delivered a throne speech in Canada just twice during her long reign, in 1957 and 1977.

Charles, making his first visit to Canada since his coronation, has never commented on Trump's repeated talk of making Canada the 51st US state.

But he will be closely watched for any comments on Canada's sovereignty, and on trade.

Trump has slapped tariffs on Canadian goods including sector-specific levies on autos, steel and aluminum, rattling the Canadian economy, although he has suspended some of them pending negotiations.

'Momentous occasion'

Queen Camilla is accompanying Charles on the 24-hour visit to Ottawa.

Carney has said his newly-elected government has been given a mandate "to define a new economic and security relationship with the United States," a neighbor he believes Canada "can no longer trust."

He has promised to curb reliance on trade with the United States by boosting internal commerce while forging deeper economic ties with allies overseas. 

The government's path to build up Canada and create new relationships will be outlined in Charles's speech, Carney said Monday.

A government statement described the visit as "a momentous and historic occasion that underscores Canada's identity and sovereignty as a constitutional monarchy."

Trump repeatedly returned to his annexation musings during Carney's Oval Office visit earlier this month, insisting it would be a "wonderful marriage."

Carney stood his ground, saying Canada was "never for sale."

Trump's envoy to Canada, Ambassador Pete Hoekstra, dismissed the notion that inviting Charles to open parliament was an effective way to make a statement on annexation. According to him, the annexation issue is "over."

But, among the throngs that showed up to welcome the royals, Robert Brown, 64, said: "I think it's a very subtle form of diplomacy. A good one."

'Once in a lifetime'

After Charles and Camilla landed in Ottawa in the afternoon, they were received by Governor General Mary Simon and other dignitaries before meeting community organizations.

They also planted a tree at the governor general's estate, and Charles held audiences with Carney and Indigenous leaders.

At the Senate on Tuesday, the monarch will receive full military honors before delivering the throne speech.

Noah Marshall told AFP he couldn't miss this "once in a lifetime opportunity to come see the royals." The 24-year-old also noted that because Trump seems to respect the King, "that's a good kind of signal to him."

Gaelle Hortop, 46, said she is "optimistic that it'll be positive for Canadian morale" too.

by Michel Comte