The prolonged disappearance of Fidel Castro from public view indicates that the Cuban president is confronting "serious" health problems, a senior State Department official said Friday.

Assistant Secretary of State Thomas Shannon, briefing reporters, also said he believes that Castro's attempt to turn over power to his brother, Raul, is doomed to fail.

"The transfer won't work," Shannon said. "Ultimately, there is no political figure inside of Cuba who matches Fidel Castro."

He added that the key to Cuba becoming a "reliable partner" in the international community is democracy.

The comments of Shannon, and those of State Department Cuba transition coordinator Caleb McCarry, were the most extensive by the administration since Castro, citing intestinal surgery, temporarily transferred power to Raul, the defense minister, on July 31.

Neither of two has been seen in public since, and official information on the Cuban president's health has been scant.

Shannon acknowledged that the administration does not know how serious Castro's condition is.

"We don't know what the level of recovery is," he said. "We're not in a position to know what the result is going to be."

Shannon seemed to brush aside Cuba's stated policy of reinstating Castro to full powers once he recovers.

He said Cuba may be at a point of "regime hardening" in an effort to ensure that the planned succession to Raul is not derailed. But he suggested that that strategy was unsustainable.

"When a supreme leader disappears from an authoritarian regime, the regime flounders," he said. "It doesn't have the direction that it requires."

When such a leader is incapacited or dead, "everybody else is frozen," he said. "It's very difficult for them (Cuban officials) to make public statements, not only about the wellbeing of Fidel Castro but also the wellbeing of the regime."

Shannon said it is imperative that the international community demonstrate a "clear show of solidarity" in support of a democratic transition in Cuba.

He welcomed a recent statement by former Costa Rican President Oscar Arias, a Nobel Prize winner, asserting that Cubans deserve a chance to choose their own leaders after 47 years of one-party rule.

Cuban spokesmen have given optimistic accounts of Fidel Castro's progress in conquering his illness. But his closest ally, Venezuelan President Hugo Chavez, said Thursday that the Cuban leader is in "a great battle for life." He also said he was confident that Castro would recover.

The United States spent $49 million last year on promoting a democratic transition and recently asked Congress for an additional $80 million.

If approved, McCarry said the funds will be spent on increasing the flow of independent information to Cuba as a means of countering the Cuban government's monopoly control over information flows.

Funds also will be spent on upgrading U.S. government radio and television stations tailored for Cuban audiences, he said.

In addition, the administration will work to permit Cubans to have uncensored access to the Internet and "to provide support for opening space for Cubans to define their own future," McCarry added.