Picture taken 23 December, 2004 of Cuban President Fidel Castro (L) being assisted to sit down by his brother Raul Castro, Minister of the Armed Forces. AFP PHOTO

"The Cuban leader will always fight until the last moment. But that last moment is very far away," National Assembly President Ricardo Alarcon said in the first word from Cuba on Castro's condition since Monday evening's announcement he was handing over power provisionally to his brother.

Monday's news that the 79-year-old Castro was undergoing surgery for gastrointestinal bleeding set off street parties in Miami by Cuban exiles who yearn for the demise of the West's only communist government.

The news also prompted speculation that Castro, who took power in 1959, would not return to office. In Washington, the Bush administration, which has tightened the decades-long U.S. embargo with Cuba, dismissed any possibility of a softer stance with new leader Raul Castro.

In Cuba, where Castro's guerrillas once swept down from the Sierra Maestra hills to overthrow a U.S.-backed dictator, word of his illness brought apprehension over the future of the Caribbean island nation of 11 million.

Opinion can be hard to measure in a tightly controlled society. But many Cubans, whether admiring or not of Castro, seemed stunned by the temporary exit from the scene of a figure who has run their lives for decades.

Castro, who last appeared in public giving a July 26 speech, said in a "proclamation" read out by an aide on television that his ill health was caused by overexerting himself during travels last month.

Castro, whose health has been an issue since he fainted during a speech in 2001, gave the reins of the ruling Communist Party, the post of commander in chief of the armed forces and president of the executive council of state to Raul Castro, 75, his constitutional successor.

CALM IN HAVANA

Cubans went about their lives calmly on Tuesday with no signs in Havana of an increased police presence. But many Cubans expressed worries about the future.

"Fidel must be in very bad shape to have handed over all powers. I pray that God helps him recover," said Carmen Vallejo, a dissident in Havana whose father was Castro's friend and doctor in the early days of the revolution.

The White House said that it did not believe that Castro was dead and that the United States had no plans to engage a Cuban government led by Raul Castro.

"Raul Castro's attempt to impose himself on the Cuban people is just much the same" as his brother, said White House spokesman Tony Snow. "There are no plans to reach out."

Venezuela, whose leftist President Hugo Chavez has become a close ally of Castro, said in a statement from its foreign relations ministry that Castro's recovery was "advancing positively," citing information from the Cuban government.

But medical experts said surgery for major bleeding in a elderly man is risky and could require several months of rest.

The news sparked wild celebrations in Miami, where many exiles view Castro as a brutal dictator whose demise could usher in a new democratic era for their homeland.

"I think there's a possibility that he may be very, very ill or dead," Cuba-born Sen. Mel Martinez, a Republican from Florida, told a news conference.

President George W. Bush, seeking to undermine a succession, has tightened enforcement of sanctions on Cuba and increased funding of its small, repressed dissident movement.

The four-decade-old U.S. embargo against Cuba is widely seen to have failed to undermine Castro, but a State Department official said there would be no change in policy because of laws restricting U.S. dealings with the communist government.

U.S. Rep. Ileana Ros-Lehtinen, a Florida Republican, dismissed talk of any diplomatic overtures from Washington.

"He's an assassin, he's a liar, he's a cheat. And the United States government is not fooled by a change of dictatorship," she said, referring to Raul Castro.

"Whether it's Fidel, whether it's Raul. A skunk is still a skunk and a dictator is still a dictator. The Bush administration is not going to be fooled."

In Cuba, concerns over Castro's increasing frailty have led the leadership to build up Raul Castro's public profile.

Castro's pace has slowed since he stumbled after a speech in 2004, fracturing a knee and an arm.

Raul lacks his brother's charismatic oratory and is more of a pragmatist who is open to economic reforms following China's model, analysts say.

In a sign of Latin America's difference with Washington over Cuba, Regional diplomatic power Brazil said it was concerned about foreign meddling in Caribbean nation after Castro stepped down.

Castro, the world's third-longest serving head of state, asked in his statement for the country to postpone celebrations of his 80th birthday until December, but said plans should not be changed for a summit in September of the Nonaligned Movement in Havana.