The Bush administration says it is carefully monitoring the situation in Cuba, after President Fidel Castro temporarily handed power to his brother while undergoing surgery.
A White House spokesman said U.S. officials will not speculate on Mr. Castro's health. He added that the United States continues to work for Cuba's freedom.
Mr. Castro released a statement Monday saying the handover is temporary. The statement said the long-time Cuban leader had surgery for gastrointestinal bleeding brought on by stress. He is expected to rest for the next few weeks. This is the first time in Mr. Castro's 47 years in power that he is known to have relinquished power.
Mr. Castro's brother and designated successor, Raul Castro, will hold presidential powers and lead Cuba's Communist Party while the president recovers.
In the U.S., Cuban exiles in Miami, Florida, are celebrating the news of the Cuban president's illness by dancing in the streets of the city's Little Havana neighborhood.
Fidel Castro turns 80 later this month. He has appeared increasingly frail in recent years and is rumored to have Parkinson's disease.
The United States has long been critical of Mr. Castro's communist regime. It has kept an economic blockade against Cuba for decades. The two countries have no diplomatic ties.
President Bush approved an $80-million program earlier this year aimed at fostering democratic change in Cuba. His administration has also pledged support for any post-Castro Cuban government that promises free elections and an end to repression.
Some information for this report was provided by AP and Reuters.