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Lynne Sladky, Associated Press
Rebecca Basulto waves a Cuban flag and American flag in the Miami neighborhood of Little Havana.

Fidel Castro's departure as Cuba's president probably will not spark immediate change in the lives of everyday Cubans or a rapid thawing of the long-frosty relations between the communist-ruled island and the United States, analysts said after Castro's announcement Tuesday.

The announcement came simply in the form of a letter posted on the Web site of the state-run newspaper, Granma. "I am saying that I will neither aspire to nor accept, I repeat, I will neither aspire to nor accept the positions of President of the State Council and Commander in Chief," Castro, 81, said.

U.S. policy is unlikely to shift until a new American president takes office in January 2009. And while Castro's designated successor, his 76-year-old brother, Raul, has called for economic reforms on the island, he has not yet announced any dramatic new initiatives, experts on Cuba said.

The Bush administration is ruling out any changes in its Cuba policy — including lifting a five-decade trade embargo — deriding Raul Castro as "dictator lite."

The next step in Cuba's unfolding new era comes Sunday, when the Cuban National Assembly meets and elects a Council of State, the island's main governing body.

The biggest surprise would be if Raul Castro is not named president but instead leaves the post to a younger leader, while retaining his position as head of Cuba's powerful military.

"I think there's a good chance a younger leader might be named," said Jonathan Brown, a Cuba expert at the University of Texas at Austin. "If I were Raul and I was interested in opening up to the outside world, I would keep my post in the army and allow others to go out on a limb with the opening."

In his autobiography, "Fidel Castro: My Life," published earlier this month by Scribner, Fidel Castro himself dropped hints that his brother might not succeed him.

"He is catching up to me in years, they keep coming, so it's also a generational problem," Castro wrote. "Already some generations are replacing others. I'm confident, but now there are new generations, because ours is passing into history."

Many experts believe a top contender is Carlos Lage, 56, vice president of the council and a longtime Raul Castro ally. A medical doctor, Lage was instrumental in drawing up economic reforms in the early 1990s during Cuba's crisis, triggered by the collapse of its longtime sponsor, the Soviet Union.

Lage's stature has risen since Fidel Castro temporarily turned over power to Raul in July 2006 after falling ill with a stomach ailment that nearly killed him. While Castro has made only a few appearances in videos and has spent his time writing long essays for Cuba's newspapers, Raul Castro has clamped down on corruption, called for increased productivity and started a national debate over Cuba's future.

Lage, meanwhile, has made high-profile trips to international events and inaugurations, a role that Cuba's image-sensitive leaders carefully control.

But other analysts say it is more likely that Raul Castro will emerge from Sunday's meeting as Cuba's new president, with Lage stepping up to first vice president and solidifying his position as Raul's successor.

"They will choose Raul Castro," said Wayne Smith, a senior fellow at the Center for International Policy and head of the U.S. Interests Section in Havana in the early 1980s. "I know there is some speculation a younger leader might be chosen, but I don't expect that. Carlos Lage will be the first vice president."

President Bush reacted to Castro's announcement by calling again for free elections in Cuba, where only candidates from the Communist Party are allowed to run for office.

"I believe the change from Fidel Castro ought to begin a period of democratic transition," Bush said from Rwanda during his African tour. "Eventually, this transition ought to lead to free and fair elections. And I mean free and fair, not these kind of staged elections that the Castro brothers try to foist off as true democracy."

Whoever takes over in Cuba will govern a population that is clearly eager for change and an improvement in living conditions.

While Cuba regularly touts its free education and health-care systems — which critics say are inadequate — the island's leaders acknowledge their economy is sluggish, productivity is low, the transportation system is woeful and workers need higher wages, which now hover between $15 and $20 a month.

"The big issue this year is whether the Cuban government, having raised expectations of economic reform, will deliver or not," said Philip Peters, a Cuba expert at the Lexington Institute. "My guess is it increases the likelihood of reforms, but we can't predict the pace or depth of those reforms."

There is also the question of how much influence Fidel Castro will continue to exert behind the scenes. Castro will apparently keep his job as head of the Communist Party.