Panama's President Moscoso is blocking the extradition

Among the four suspected of trying to kill President Castro is Luis Posada Carriles, who the Cubans have wanted for many years.

He is accused of a string of offences, including an attack on a Cuban passenger plane which crashed off the coast of Barbados in 1976.

Last November's alleged assassination attempt was the latest in what the Cuban authorities say have been hundreds of attempts on the life of President Castro since he came to power in 1959.

Exiles in the US

The authorities usually blame Cuban exiles in the United States who they say receive the backing of the American authorities.

Mr Carriles, they say, is merely one of the more active of many Cuban exiles plotting against the island's communist government.

The Cubans thought he was almost in their grasp when the Supreme Court in Panama ruled in February that the detention of the four men was legal and implied that extradition proceedings would go ahead.

The Cuban Foreign Ministry says Cuban exiles and representatives from the US have recently been to Panama to call for the men's release.

Many in Miami see them as heroes battling to overthrow more than 40 years of Communist rule in Cuba.