HAVANA — Fidel Castro temporarily relinquished his presidential powers to his brother Raul on Monday night and told Cubans that he had undergone surgery.
The Cuban leader said he had suffered intestinal bleeding, apparently due to stress from recent public appearances in Argentina and Cuba, according to the letter read live on television by his secretary, Carlos Valenciaga.
Castro said that extreme stress "had provoked in me a sharp intestinal crisis with sustained bleeding that obligated me to undergo a complicated surgical procedure."
Castro said he had undergone surgery and was temporarily relinquishing the presidency to his brother and successor Raul, the defense minister.
He said the move was of "a provisional character."
He said celebrations scheduled for his 80th birthday on Aug. 13 were to be postponed until Dec. 2, the 50th anniversary of Cuba's Revolutionary Armed Forces.
Castro said he would also temporarily relinquish his duties as first secretary of the Communist Party of Cuba to Raul, who turned 75 in June and who has been taking on a more public profile in recent weeks.
In power since the triumph of the Cuban revolution on Jan. 1, 1959, Castro is the world's longest ruling head of government. Only Britain's Queen Elizabeth, crowned in 1952, has been head of state longer.
Castro has defied America for nearly half a century, resisting U.S. attempts to topple him while wielding almost absolute control over the communist state he built just 90 miles south of Florida.
Through 10 U.S. administrations beginning with that of Dwight Eisenhower, he has survived assassination attempts, an invasion by a CIA-trained exile army at the Bay of Pigs, and a standoff with Washington over Soviet missiles that pushed the world to the brink of nuclear war.
His iron-clad rule has ensured Cuba remains among the world's five remaining communist countries. The others are all in Asia: China, Vietnam, Laos and North Korea.
Over nearly five decades, hundreds of thousands of Cubans have fled Castro's rule, many of them settling just across the Florida Straits in Miami.
Castro rose to power after an armed revolution he led drove out then-President Fulgencio Batista.
The United States was the first country to recognize Castro, but his radical economic reforms and rapid trials of Batista supporters quickly unsettled U.S. leaders.