King Charles has insisted differences are a "source of strength"

In a preview of his speech, the king said: "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.

"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."

Charles' full message for Commonwealth Day will be printed in the order of service for Monday afternoon's service at Westminster Abbey, which will have the theme 'Together We Thrive'.

As well as the king and his wife, Queen Camilla, the Prince and Princess of Wales, Princess Anne, and the Duke and Duchess of Gloucester are also due to be part of the 2,000-strong congregation.

In October, Charles urged the Commonwealth to find "creative ways to right inequalities that endure".

Speaking during the opening ceremony for the Commonwealth Heads of Government Meeting in Apia, he said: "None of us can change the past. But we can commit, with all our hearts to learning its lessons and to finding creative ways to right inequalities that endure.

"Nothing, it seems to me, would do so more decisively than to champion the principle that our Commonwealth is one of genuine opportunity for all.

"It is vital, therefore, that we understand our history -to guide us to make the right choices in the future. Where inequalities exist, for example, in access to opportunity; to education; to skills training; to employment; to health; and to a planet in whose climate our human race can both survive and thrive, we must find the right ways, and the right language, to address them.

"As we look around the world and consider its many deeply concerning challenges, let us choose within our Commonwealth family the language of community and respect, and reject the language of division."