In the annual message to mark the day on Monday, the King will emphasise the value of nations coming together in a “spirit of support, and crucially, friendship”.

The King has become involved in the diplomatic negotiations involving the UK, the US and Ukraine – with the monarch warmly welcoming President Volodymyr Zelensky after the Ukrainian leader’s disastrous meeting with US President Donald Trump and with a state visit planned for Trump.

A Commonwealth country, Canada, also faces its own tensions with Trump’s administration, as he has called for Canada to become the US 51st state.

Commonwealth Day is traditionally marked with a service at Westminster Abbey and this year the King and Queen will attend alongside the Prince and Princess of Wales.

In his written message, which will be published in full on Monday, the King will say: “In these uncertain times, where it is all too easy to believe that our differences are problems instead of a source of strength and an opportunity for learning, the Commonwealth’s remarkable collection of nations and peoples come together in the spirit of support and, crucially, friendship.”

It is a message that he has made before – that the diversity of peoples and cultures is a strength and not a weakness.

But it is a message now against a backdrop of global tensions, as the US pushes for an end to the war that followed the Russian invasion of Ukraine.

As well as a show of solidarity with the Ukrainian President Zelensky, the King this week held a meeting with Canadian PM Justin Trudeau, a Commonwealth leader who has faced pressure from the US.

King Charles is Canada’s head of state and ahead of the meeting Trudeau said: “Nothing seems more important to Canadians right now than standing up for our sovereignty and our independence as a nation.”

The King used the Commonwealth, with its 56-member nations, as an example of co-operation between countries.

“The Commonwealth’s ability to bring together people from all over the world has stood the test of time and remains as ever-important today,” says the King’s message.

The service at Westminster Abbey on Monday will emphasise the multicultural diversity of the Commonwealth, with the royal guests being met by a pipe band from a Hindu eco-temple in north-west London.

There will be music from an African arts group, the Masai Cultural Arts team.

And singer Joan Armatrading will perform a version of her song, Love and Affection.

An innovation for this year’s Commonwealth Day has been that the King has prepared his own personal playlist of favourite music tracks, by artists including Bob Marley, Kylie Minogue and Raye.