The CIA has claimed that Cuban President Fidel Castro suffers from Parkinson's disease and could have difficulty coping with the duties of office as his condition worsens.
The assessment, completed in recent months, suggests the non-fatal but debilitating disease has progressed far enough to warrant questions among US policymakers about the communist country's future in the next several years.
Bush administration officials and members of Congress have already been briefed on the findings about Castro. The Cuban leader (79) has been in power on the island of 11 million people since leading a 1959 revolution and has long been at ideological odds with Washington.
US diplomats played down the significance of any CIA assessment and said they were not using such intelligence to make policy decisions about Castro or Cuba.
Castro has long been the subject of rumours of illnesses - including Parkinson's - and many of the reports up to now have come from the anti-communist Cuban American community in Florida.
Castro's brother Raul, head of the armed forces, has been designated as his successor and the Cuban leader has insisted that he expects Cuba's political system to outlive him.
Cuba and the United States have no diplomatic relations, and the United States imposed an economic embargo on Havana 43 years ago.