By Nick Caistor BBC World Service and Radio 4's Crossing Continents

As President Fidel Castro nears 80, people both within and outside Cuba are speculating - and in some cases planning for - the succession.

Cuban President Fidel Castro is the world's longest-serving leader

"Fidel is like a father to me," says Adalaida. "He's been with me all my life, and he and the revolution have given me all I have."

Adalaida is busy sweeping the concrete porch outside the whitewashed wooden shack she shares with her husband Jose, deep in the Cuban countryside.

Jose is a member of a farming co-operative in Pinar del Rio, which like many others, produces tobacco for Cuba's famous cigars.

Although they earn much less each month than a box of cigars costs in the tourist hotels, the couple say they are happy, especially as now they have their own plot of land to grow vegetables and rice, which they use both for their own consumption and to sell at the local farmers' market.

When he dies, it'll be terrible for me Adalaida

But Adalaida is worried. She knows Fidel is growing old. Like many people in Cuba today, she wonders what will happen to her life and the revolution once he is no longer in charge.

"Whenever he doesn't appear on the television, I'm afraid something has happened to him. When he dies, it'll be terrible for me," she says.

Smooth transition?

Now fast approaching 80, President Castro has run Cuba's socialist revolution since it began in 1959.

He is still the one all the Communist Party faithful look to for the inspiration and ideas to keep the revolution going.

There are plans for Raul Castro (right) to succeed his brother

One of his staunchest supporters is Kenia Serrano, a member of the National Assembly and a Communist Party leader.

She says she does not think there will be a huge upheaval when Fidel goes.

"The succession has been prepared," she insists. "The first vice-president is Raul [Fidel's younger brother, the head of Cuba's armed forces].

"And beyond him, we have a leadership who have learnt from Fidel what is needed to continue to build the revolution."

Opposition's fears

Others in Cuba are not so sure there will be such a smooth transition.

"After Fidel, there is a huge risk of instability and chaos," says Osvaldo Paya. He is the head of a small opposition group known as the Christian Liberation Movement.

It is not only people on the island who are planning for Cuba's future Send us your comments

Among the 75 dissidents rounded up in March 2003 and sentenced to lengthy prison terms are members of Mr Paya's group.

Mr Paya says that the state security forces have threatened that when the president dies he himself will be arrested and killed.

In order to prevent the risk of an explosion of violence on the president's death, Mr Paya supports engaging in dialogue now, in the hope of promoting a peaceful transition to a more democratic system.

But it is not only people on the island who are planning for Cuba's future after Fidel Castro.

US plans

In Washington, the Bush administration has appointed Caleb McCarry as "transition co-ordinator" for Cuba.

He says his job is to help Cubans "recover their freedom after 47 years of brutal dictatorship".

To achieve this, Mr McCarry has a budget of $59m to "hasten the transition" and to ensure that neither Raul Castro nor any of the other "pretenders", from Vice President Carlos Lage to Foreign Minister Perez Roque, automatically continue the current system.

We are providing support for a process of transition that helps Cubans recover their sovereignty Caleb McCarry, US transition co-ordinator

"They are planning for a continued dictatorship," says Mr McCarry.

"We are providing support for a process of transition that helps Cubans recover their sovereignty and hold free and fair elections."

As well as these official initiatives, many in the Miami Cuban-American exile community are already dreaming of a return to Cuba.

These range from Lombardo Perez, who is drawing up plans for car dealerships throughout the island, to Jose Cancela, a media consultant who says he has pledges of up to a billion dollars from people interested in investing in the media of a non-Communist Cuba.

Armed intervention?

Others in the Miami Cuban community are still hoping that the US will not wait for a natural end to Fidel Castro's days in power.

According to a recent poll, as many as one in three of those questioned said they would favour armed intervention by the US to bring about regime change in Cuba.

"How come the US went so many miles from our shores to get rid of a tyrant, and they don't understand the risk of having somebody spreading communism and violence around this hemisphere?" complains Remedios Diaz, a business woman who is one of the founders of the Cuban Liberty Council.

If there is an intervention, we will fight immediately Kenia Serrano, Cuba National Assembly

She looks forward to a day soon when she can market her products freely throughout Cuba, and is not worried if change there is brought about by force.

To most though, the idea of armed conflict is the worst possible scenario for any transition after Castro.

Dissident voices in Cuba stress that there must be dialogue and reconciliation, and that changing Cuban society to a more open, Western-style democracy needs to be undertaken gradually.

For her part, National Assembly member Kenia Serrano sounds a warning on behalf of all those who still believe in Fidel Castro's revolution: "If there is an intervention, we will fight immediately.

"In every neighbourhood, in every corner of this country, we are going to have people ready to fight."

After Castro will be broadcast on the BBC World Service from Wednesday, 12 April, 2006.

BBC Radio 4's Crossing Continents was broadcast on Thursday, 13 April, 2006 at 1102 BST and repeated on Monday, 17 April, at 2030 BST.