Queen Elizabeth II is to miss the Commonwealth heads of government meeting this year for the first time in 40 years, Buckingham Palace said Tuesday, dpa reported.
The 87-year-old head of the Commonwealth is to be represented by her heir Prince Charles at the meeting, which is to be held in November in Sri Lanka.
"The reason is that we are reviewing the amount of long-haul travel that is taken by the queen," a spokesman said.
The queen missed the first such meeting in 1971 but attended the second, held in Canada in 1973, and has been present at every one of the biennial meetings since.
The step is a significant one for Charles because it is not automatic that he would become head of the Commonwealth if he succeeds the queen as monarch.
The media has recently speculated over the health of the queen after she was admitted to hospital in March with a stomach bug although she has since appeared to make a full recovery.
The Commonwealth, a voluntary association of 54 countries that evolved from the British Empire, was established in 1949 after India and Pakistan were granted independence.
The queen has no formal powers over its members, which have a combined population of 2 billion people.