King Charles III and Queen Camilla will arrive in Canada later, for a two-day visit seen as bringing a message of support for the country in the face of threats and taunts from US President Donald Trump.

Prime Minister Mark Carney, who recently won a general election on a wave of anti-Trump sentiment, invited the royal couple and will hold a meeting with them during their stay in Ottawa.

The King will read the "Speech from the Throne" to Canada's Parliament on Tuesday, the first time a monarch has delivered this for almost 50 years.

It is expected to include a defence of Canada's sovereignty and to reject claims it should be taken over by the US.

There will be a ceremonial welcome at the airport in Ottawa on Monday and meetings with community groups, which are expected to include representatives of Canada's First Nation communities.

The King will meet Canada's first indigenous Governor General Mary Simon.

This is the King and Queen's first visit to Canada since the start of their reign, after a planned trip last year was cancelled because of King Charles's cancer diagnosis.

By reading the Speech from the Throne the King is following in the footsteps of his mother, Queen Elizabeth II, who carried out the duty twice during her long reign in 1957 and 1977.

But the timing of this week's visit has been seen as a sign of solidarity with Canada, after calls from Trump for the country to become the 51st US state.

The US threat has inflamed public opinion with some businesses in Ottawa, as elsewhere in Canada, putting on displays of national identity such as "Proudly Canadian" posters.

Carney, when he visited Trump at the White House earlier this month, stressed that Canada was "not for sale" and that message is likely to be conveyed in the King's speech which is written on the advice of Canada's government.

Former Canadian high commissioner to the UK Jeremy Kinsman said this was a message the King will be pleased to deliver.

"It's going to be very affirmative of Canadian sovereignty. And I can say personally that it's something that King Charles will celebrate saying. I have no doubt," said Mr Kinsman, who worked as a diplomat with the King when he was Prince of Wales.

The speech, to be delivered in French and English, will set out the Canadian government's policy agenda in a way that is similar to the King's Speech at the State Opening of Parliament in Westminster.

But it is also expected to have lines asserting the independence of Canada - a Commonwealth country and Nato member.

Speaking ahead of the King's visit and State Opening, Carney said: "This is an historic honour which matches the weight of our times."

In terms of the ceremony, the King is expected to wear a suit, in an event that will be more low key than the crown and elaborate robes on display in the UK's opening of Parliament.

As well as the speech in Parliament, this brief trip will include community events in Ottawa and a chance to meet local leaders.

This royal visit will be something of a diplomatic balancing act. The King is head of state of both Canada and the UK - and in his UK role, the King has been helping to maintain good relations with the US, sending a warm personal letter to President Trump inviting him for a second state visit.

In Canada, he will be expected to reflect a very different message, with Canada's government rejecting Trump's ambition to take over the country.

Ahead of the visit, a royal source said: "The King has long experience and great skill in walking that diplomatic tightrope.

"He's held in high regard around the globe and across the political spectrum, with good relations with world leaders who understand his unique position."