HAVANA, Cuba (AP) - An ailing 81-year-old Fidel Castro resigned as Cuba's president yesterday after foiling US attempts to topple him for nearly half-a-century - leaving on his own terms by clearing the way for his brother Raul to take power.

The end of Castro's rule - the longest in the world for a head of government - frees 76-year-old Raul to implement reforms he has hinted at since taking over as acting president when Fidel Castro fell ill in July 2006. US President George W Bush rejected any Castro in power, hoping for what he called a democratic transition.

Castro. it would be a betrayal to my conscience to accept a responsibility requiring more mobility and dedication than I am physically able to offer

"My wishes have always been to discharge my duties to my last breath," Castro wrote in a letter published yesterday in the online edition of the Communist Party daily Granma. But, he wrote, "it would be a betrayal to my conscience to accept a responsibility requiring more mobility and dedication than I am physically able to offer."

It wasn't until 5:00 am, several hours after Castro's message was posted on the Internet, that official radio began spreading the news across the island. Cubans seemed to go about their business as usual, having seen Castro's resignation as inevitable, but with a certain sadness.

"It is like losing a father," said Luis Conte, an elderly night watchman at a museum. Or "like a marriage - a very long one that is over."

Cuban dissidents welcomed the news as a possible first step toward possible change.

Moderate opposition leader Eloy Gutierrez Menoyo, a former commander who fought alongside Castro in the revolution, expressed hopes that whoever follows Fidel "will have freedom to launch economic and political changes as well".

"History will say if it is a good day, depending upon what happens," added Oswaldo Paya, whose pro-democracy Varela Project sought an unsuccessful referendum on civil rights and electoral reforms.

"The change of a person does not signify the change of a system," Paya noted, but said Cubans are ready for peaceful changes. "We have always maintained hope, and today we are more hopeful because the people are vibrating" with emotion, he said.

Castro temporarily ceded his powers to his brother on July 31, 2006, after undergoing intestinal surgery. Since then, the elder Castro has not been seen in public, appearing only sporadically in official photographs and videotapes and publishing dense essays about mostly international themes as his younger brother has consolidated his rule.

There had been widespread speculation about whether Castro would continue as president when the new National Assembly meets Sunday to pick the country's top leadership. Castro has been Cuba's unchallenged leader since 1959 - monarchs excepted, he was the world's longest ruling head of state.

Castro said Cuban officials had wanted him to remain in power after his surgery.

"It was an uncomfortable situation for me vis-a-vis an adversary that had done everything possible to get rid of me, and I felt reluctant to comply," he said in a reference to the United States.

Castro remains a member of parliament and is likely to be elected to the 31-member Council of State on Sunday, though he will no longer be its president. Raul Castro's wife, Vilma Espin, maintained her council seat until her death last year even though she was too sick to attend meetings for many months.

Castro also retains his powerful post as first secretary of Cuba's Communist Party. The party leadership posts generally are renewed at party congresses, the last of which was held in 1997.

"He will continue to be my commander in chief. He will continue to be my president," said Miriam, a 50-year-old boat worker waiting for a bus who, like most Cubans, was reluctant to give her full name to a foreign journalist. "But I'm not sad because he isn't leaving, and after 49 years he is finally resting a bit."

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