The revolutionary leader has been out of public view for three years after standing down for health reasons and handing power to his younger brother Raul.

It is believed he is still consulted on major decisions but his role in day-to-day government of the island is unclear.

Dr Kevin Wagner, political scientist at Florida Atlantic University, told Sky News: "We simply don't know if he still has any power because it is very hard to tell what is going on inside the Cuban government.

"It is hard to analyse a government which is simply not covered by a free press."

Castro led the 1959 revolution that overthrew President Batista and ran the country for 49 years before he underwent emergency surgery in July 2006.

He has been seen only in videos and photographs with visiting leaders since then but has written almost 250 columns for state-run media.

Castro has become an increasingly remote figure for young people in Cuba, particularly with the country facing its worst economic crisis for decades.

Construction worker Raul Gonzalez said: "Fidel is very intelligent but he can't admit he made a mistake by giving Cuba a system that never worked."

It is different for Cubans who remember the revolution.

Cicero Argent, a 63-year-old security guard, said: "Fidel Castro has given us stability.

"Maybe things are a little difficult right now but we don't have a drug problem, we don't have a lot of crime like in other countries."

Castro has played down overtures from US President Barack Obama to improve ties with Havana.

In April, he wrote: "The adversary should never be under the illusion that Cuba will surrender."

Obama has said he will keep the 47-year-old US trade embargo in place to press the Cuban leadership to improve human rights and grant political freedoms.

Dr Wagner said: "The Obama administration has made significant movement towards being more open.

"Once Castro has gone there will be definitely a softening of US policy towards Cuba."

Source: Sky News