According to the country’s vice president Castro, who turns 80 on Sunday, could resume presidential functions within weeks but another top official spoke of months, reflecting the secrecy surrounding the ailing president's condition.
Few details of Castro's health have emerged since a television message on July 31st in which the Cuban president announced he had undergone surgery for intestinal bleeding.
He handed over power to his brother Raul, his designated successor and Cuba's defence minister.
Asked when the communist leader would reassume the leadership Vice President Carlos Lage said: "in weeks, as he himself says."
Speaking to journalists in Bogota, Lage said Castro was "conscious at all times" and was being well cared for at a hospital.
"A few hours ago, a friend who spent time with the commander and was impressed by his recovery.”
But Roberto Fernandez Retamar, a member of Cuba's Council of State, estimated it would take "several months" before Castro resumes his presidential functions.
More than three million Cubans participated in a total of 80,000 demonstrations of support for Fidel and Raul Castro over the past days, according to the country's official trade union federation.
US President George W. Bush admitted he is in the dark about the Cuban leader’s condition.
"The only thing I know is what has been speculated. And that is that he is very ill. On the other hand he's going to be coming out of hospital. I don't know."
President Bush said that Cubans "on the island" ought to decide their own future after ailing Fidel Castro gives up power, sending a strong signal to US-based Cuban exiles to stay on the sidelines for now.
"Our desire is for the Cuban people to be able to choose their own form of government," said Bush.
But Cuban-American groups in Miami rejected Bush's view, saying they would not wait for the end to Castro's regime to involve themselves in the island's politics.
"Cuban-Americans have an interest in every aspect of transition in Cuba and what all of that involves," said Camila Ruiz of the Cuban-American National Foundation.
In Havana, Retamar ridiculed what he said was Washington's conviction that Cuba without Castro would plunge into chaos.
"Fidel is not at the head of Cuba and chaos has not taken over the country."
He made the comments during the presentation of a document signed by 400 international personalities who urged the US administration to respect Cuba's sovereignty.
"We must at all cost prevent a new aggression," the document said.
The signatories include seven Nobel Prize laureates, among them South Arica's Desmond Tutu and Nadine Gordimer, as well as Nigeria's Wole Soyinka.