LONDON, April 19 (Xinhua) -- Queen Elizabeth told the heads of more than 50 states Thursday that she wants the heir to the British throne, her eldest son Prince Charles, to succeed her as head of the Commonwealth.

The British monarch made her plea at Buckingham Palace where she hosted the opening ceremony of the 2018 Commonwealth Heads of Government meeting.

Although Queen Elizabeth succeeded her late father, King George VI, as head and has led the Commonwealth since the 1950s, there is no written rule that the job should automatically go to the serving British monarch.

Royal commentators described the Queen's comments as a rare intervention, just days ahead of her 92nd birthday this weekend.

The heads of governments will be debating the succession of their head when they hold a private retreat Friday at Windsor Castle.

The Commonwealth is an intergovernmental organization of 53 member states that are mostly former territories of the British Empire, with a combined population of 2.4 billion, a third of the world's population.

In her speech, the Queen said: "It is my sincere wish that the Commonwealth will continue to offer stability and continuity for future generations, and will decide that one day The Prince of Wales should carry on the important work started by my father in 1949."

Hannah Furness, royal correspondent at the Daily Telegraph newspaper, said the message from the Queen was the clearest signal yet about the future of the head of the commonwealth.

"Her highly significant speech, met with warm applause, is the most explicit statement she has made to date of her hopes for the Commonwealth's future, and the honorary and not hereditary position of its head," wrote Furness.

British Prime Minister Theresa May, speaking at the opening ceremony, said the meeting was taking place at a time of significant global challenges.

"The rules-based international system, which has consistently delivered both prosperity and peace, faces threats in many forms and on many fronts," said May.

"Climate change and extreme weather continue to take lives and damage livelihoods across the Commonwealth. And the new opportunities afforded by the digital world have brought with them new risks, with our cyber security under attack from individuals and state actors."

May has called on commonwealth countries to join in the fight against plastic pollution. She cited the decision by the British government to end the sale of plastic straws, drink stirrers and plastic-stemmed cotton buds.

May urged Commonwealth countries to join a newly-formed Clean Oceans Alliance and take action, with bans on microbeads, a commitment to cutting down on single use plastic bags, or other steps to eliminate avoidable plastic waste.