King Charles III is expressing his gratitude to the people of the Commonwealth for both their achievements and their support as he undergoes treatment for an undisclosed form of cancer.

The United Kingdom's annual Commonwealth Day celebrates the connection, however under threat, between the monarchy and the various nations it remains linked to, such as Australia, India and several Caribbean islands and African countries.

To commemorate the day, Charles released a videotaped speech on Monday, which was recorded last month in Windsor Castle.

"In recent weeks, I have been most deeply touched by your wonderfully kind and thoughtful good wishes for my health and, in return, can only continue to serve you, to the best of my ability, throughout the Commonwealth," he said. "My belief in our shared endeavors and in the potential of our people remains as sure and strong as it has ever been. I have no doubt that we will continue to support one another across the Commonwealth as, together, we continue this vital journey."

The 2024 theme of Commonwealth is "One Resilient Common Future: Transforming our Commonwealth," according to Buckingham Palace.

"The 75th anniversary of the Commonwealth is a moment to reflect on the remarkable journey that our unique family of free and independent nations has made since 1949," Charles said at the start of his speech.

The monarch said the Commonwealth remains strong "through friendship," adding, "the Commonwealth is like the wiring of a house, and its people, our energy and our ideas are the current that runs through those wires. Together and individually, we are strengthened by sharing perspectives and experiences, and by offering and borrowing the myriad ways we have each tackled the challenges of our time."

Charles praised the "diversity" of the Commonwealth as its "greatest strength" because it brings "different experiences, knowledge, and aspirations."

"Wherever we live, we are united by the many challenges we face – whether it be climate change, the loss of nature, or the social and economic changes that new technologies are bringing," he continued. "All of this means that we must work together to understand each other’s perspectives, including the inequalities and injustices which still resonate to this day."

The British leader added: "We must find ways of healing, and to support each other to pursue solutions."

Charles concluded his speech by emphasizing the importance of the youth "who make up two-thirds of the entire Commonwealth population."

"Whether in Kenya or Malaysia, Vanuatu or Dominica, Malta, or Canada, I never cease to be impressed by their creativity, innovative skills and hard work, often in the most challenging circumstances," he said.

Prince William, Queen Camilla to co-host Commonwealth Day amid King Charles' absence

Charles is notably absent from making a physical appearance during Commonwealth Day.

Prince William, Camilla are taking leadamid King Charles' absence. Is it sustainable?

On March 3, Buckingham Palace announced that Camilla and William will helm responsibilities for the day at Westminster Abbey alongside other royals.

Princess Anne, Prince Edward and Queen Elizabeth II's cousins Prince Richard and Prince Edward, Duke of Kent, are among the working royals to be in attendance.

The public will be paying extra attention to how the family is coping and will be a key indicator if Britons still have faith in the monarchy.

"There will be increased scrutiny of the royal family at the Commonwealth Day service as this is an occasion that brings the working members of the royal family together," Carolyn Harris, co-editor of "English Consorts: Power, Influence and Dynasty" and a professor at the University of Toronto School of Continuing Studies, previously told USA TODAY.

Contributing: Jay Stahl and Marco della Cava, USA TODAY; The Associated Press

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