WASHINGTON — Deputy Secretary of State John Negroponte said Tuesday the United States will not soon lift its embargo on Cuba despite Fidel Castro's resignation.

Asked by reporters at the State Department if Washington planned to change its Cuba policy now that Castro has stepped down, Negroponte replied: "I can't imagine that happening anytime soon." He declined further comment.

The centerpiece of American policy toward Cuba has been the economic embargo, first instituted in limited form in 1960 and strengthened in 1962. Castro persistently called the trade embargo "criminal," and claimed that its economic impact on the island ran well into the tens of billions of dollars.

In Rwanda, President Bush expressed hope that the end of Fidel Castro's presidency will launch a transition to democracy in Cuba after nearly 50 years of ironclad, communist rule.

Long a target of U.S. criticism and sanctions, the ailing Castro, 81, announced he would not accept a new term.

"What does this mean for the people in Cuba?" Bush said at a news conference during his trip to Africa. "They're the ones who suffered under Fidel Castro. They're the ones who were put in prison because of their beliefs. They're the ones who have been denied their right to live in a free society. So I view this as a period of transition and it should be the beginning of the democratic transition in Cuba."

Bush said he anticipates debate about Cuba's future, and that some people will say "Let's promote stability."

"In the meantime, political prisoners will rot in prison and the human condition will remain pathetic in many cases," he said.

Bush noted that he had met with the families of some of prisoners, and that their release should be the first step of any transition to democracy.

"It just breaks your heart to realize that people have been thrown in prisons because they dare speak out," he said.

While Bush expressed hope for democratic change, Castro's decision appeared to position his brother, Raul, 76, to succeed him as president.

"The international community should work with the Cuban people to begin to build institutions that are necessary for democracy," Bush said.

"Eventually, this transition ought to lead to free and fair elections — and I mean free, and I mean fair — not these kind of staged elections that the Castro brothers try to foist off as true democracy," Bush said.

"The United States will help the people of Cuba realize the blessings of liberty," Bush said.