President George W. Bush last night branded the Castro government a "disgraced and dying order" and urged Cubans to push for democratic change.
Mr Bush also defended the decades-old policy of tight US economic sanctions on Havana in his first speech on Cuba since an ailing Fidel Castro handed power to his brother Raul in July of last year.
Cuban Foreign Minister Felipe Perez Roque
He rejected any easing of the sanctions without a full move to democracy and said doing so would only bolster the communist government's grip on power.
Mr Castro (81), is suffering from an undisclosed intestinal illness and has not been seen in public in 15 months. Many analysts believe a stable transfer of power to Raul Castro has already taken place, and some predict slow, modest changes could occur under his rule.
But Mr Bush said the handover to Raul Castro amounted to merely "exchanging one dictator for another."
"America will have no part in giving oxygen to a criminal regime victimising its own people," Mr Bush said in a speech at the State Department in Washington, DC, where he appeared with family members of Cuban political prisoners. "We will not support the old way with new faces, the old system held together by new chains."
Cuba reacted by accusing Mr Bush of inciting a violent uprising by giving more importance to liberty than stability, and said the US president had no moral authority after the bloodshed in Iraq.
"You will never force us to our knees," Cuban Foreign Minister Felipe Perez Roque said in response to the speech, which he called "gross meddling" in Cuba's internal affairs.
Mr Bush's speech reflected frustration with his plan for "regime change" in Cuba as his presidential term nears its end, Mr Perez Roque said in Havana. "You are not a liberator, Mr Bush. You are a brutal repressor," he said.