Cuba has dismissed a broadcast message from US Secretary of State Condoleezza Rice to its people urging them to push for democracy.
Cuba's official paper says Raul Castro is firmly in charge
In a message that went out on US-funded Radio and TV Marti, Ms Rice said all Cubans who "desire peaceful democratic change" could count on US support.
But Cuban Culture Minister Abel Prieto said her comments held "no value".
President Fidel Castro, 79, temporarily ceded power to his brother, Raul, on Monday after falling ill.
He was recovering "satisfactorily" from stomach surgery, Health Minister Jose Ramon Balaguer said on Friday.
Neither brother has been seen in public since Monday's announcement, provoking intense speculation about the island's future.
Ms Rice said, in her message beamed to Cuba on Friday, that "much is changing there" and echoed President Bush's calls for a democratic transition on the island.
"The United States respects your aspirations as sovereign citizens and we will stand with you to secure your rights - to speak as you choose, to think as you please, to worship as you wish, and to choose your leaders freely and fairly in democratic elections," she said.
The Cuban government tries, largely successfully, to block US broadcasts to the island, the BBC's Nick Miles in Washington reports.
But Cubans who did hear Ms Rice's message will notice a hands-off approach from America, he adds.
She called for Cubans to work at home for change - clearly hoping for a peaceful transition that avoids the risk of a huge refugee crisis, our correspondent points out.
Mr Prieto said Ms Rice's words would fall on deaf ears, and called on Washington to "respect the institutions of this country".
"Condoleezza knows perfectly well that no-one in Cuba will hear her message, which comes from a foreign government official, which is of no value to Cubans," he said.
Cuba's communist leadership has assured Cubans that Raul Castro is firmly in charge of the nation.
The lead story in Friday's edition of the official newspaper, Granma, declared that Raul Castro was at the helm of the nation and of the armed forces.
The paper also printed a half-century-old photograph of Raul as a 22-year-old man, shortly after he was arrested in the early years of the Cuban revolution, and recounted his exploits in heroic terms.
The paper was also dismissive of President Bush's call for a transition to democracy in Cuba, saying "transition is not in the vocabulary of Cubans".
The BBC's Stephen Gibbs in Havana says one theory behind Raul Castro's non-appearance is that he is deliberately giving Cubans time to adjust to the reality that, at least temporarily, the only leader they have known for the last 47 years is out of action.
Fidel Castro - who turns 80 this month - is one of the world's longest-ruling leaders, and has outlasted nine US presidents.
The US imposed an embargo on the Caribbean island in 1962 - three years after Mr Castro took power - which remains in place.