By Jeff Franks
HAVANA (Reuters) - Cuban President Raul Castro turns 80 on Friday, the head of an aging government trying to preserve one of the world's last communist systems.
At a time when most men have settled into retirement, Castro is directing a significant reform of Cuba's struggling economy while simultaneously casting about for younger leaders to replace him and his octogenarian colleagues.
He has said many times he wants to ensure that Cuban communism goes on after the current leadership, in power since Cuba's 1959 revolution, is gone.
Only time will tell if he achieves his goal. But by his own admission there are no overnight cures for Cuba's economic malaise, meaning time is not particularly on his side.
"Days and years of intensive work and great responsibilities lie before us to preserve ... the independent and socialist future of our homeland," he said at an April congress of the ruling Communist Party.
Raul Castro will be 80, his No. 2, Jose Machado Ventura, is 80 and his No. 3, Ramiro Valdes, is 79.
Older brother Fidel Castro, who led the Caribbean island for 49 years, is 84 and officially out of the picture, but still has his brother's ear and behind-the-scenes political clout.
They are old men fighting for what began as the dreams of young men.
Fidel Castro was 32 and Raul Castro just 27 when they took over Cuba and set about making it a communist state at the doorstep of the United States.
But after half a century of economic struggle -- some of it the product of a longstanding U.S. trade embargo and some of inefficiencies in the socialist system -- Raul Castro is making changes.
STEALING FROM CAPITALISM
Stealing lightly from capitalism, he has put in place policies encouraging more private initiative and providing more financial incentive for productive workers, with the aim of boosting the debt-ridden, Soviet-style economy.
He wants to give state companies more autonomy, has put more agriculture in private hands and plans to slash a million jobs from government payrolls.
But change only goes so far. Guidelines approved at the party congress reaffirmed central planning for the economy and said accumulation of property would not be allowed.
Raul Castro admitted at the congress that the government has not groomed younger replacements for its leaders, which he said was "really embarrassing."
He pledged to address the succession issue and said a party conference next January would consider limiting future leaders to a maximum of two five-year terms.
The result of all this is that Fidel Castro used to be considered the indispensable heart of Cuban communism, but now Raul Castro has that role.
"Interruption in his rule would send a ripple through the leadership circle and the chain of command since they are all of his choosing and of his generation, with few truly prepared and well positioned young leaders below him," said Christopher Sabatini, senior policy director at the Americas Society in New York.
That would open up "the risk that the regime may in fact be very brittle," he said.
Many thought a similar scenario would happen when Fidel Castro left power due to illness in 2006, but with his brother waiting in the wings, a smooth transition occurred.
Raul Castro's challenge is to find younger blood who can lead Cubans and is dedicated to socialism.
There has been speculation power will stay in the family, with one of his children a likely successor or possibly son-in-law Luis Alberto RodrÌguez Lopez Callejas, who heads GAESA, a military company with extensive business holdings.
Ideological fealty will be the key, Sabatini believes.
"Loyalty will be the most important trait they will be looking for," he said. "They need to look for someone loyal and younger, though when you're 80 it's all relative."
(Editing by Cynthia Osterman)