A Cuban newspaper has published the first photos of Cuban President Fidel Castro since the announcement July 31 that he underwent surgery for intestinal bleeding, and his younger brother, Raul, appeared in public for the first time since assuming temporary leadership. Both developments coincided with Fidel Castro's 80th birthday.

A message from Mr. Castro accompanied the photographs in the Juventud Rebelde newspaper.

He is quoted as saying he feels very happy, and calls for Cubans to be optimistic about his health.

But he also says they should be ready to face any adverse news. He did not elaborate, but says his recovery will take time, and that there are still risks.

The photographs show the communist leader in a red-and-white striped athletic jacket. In two of the pictures, he is on the telephone, and in another he is holding up Saturday's tribute to him published by the Communist Party Granma newspaper. The fourth photograph is a close-up.

Official celebrations for Mr. Castro's birthday have been postponed at his request, until December second, the 50th anniversary of Cuba's Revolutionary Armed Forces.

Venezuelan President Hugo Chavez arrived in Cuba to visit Mr. Castro and celebrate the birthday with his ally and fellow critic of the United States.

Mr. Chavez was greeted at the airport by Raul Castro. It was the first time Raul was seen in public since he assumed temporary power, due to his brother's health, two weeks ago.

Cuban officials say Fidel Castro, who seized power in 1959, is recovering well. The United States said Friday that more may be happening on the island than what Havana is saying.

The State Department's senior official for Latin America, Thomas Shannon, told reporters Friday in Washington he believes the developments in Cuba may indicate that Mr. Castro is suffering serious health problems, and political change may be occurring.

"Authoritarian regimes are like helicopters, they are 'single fail-point' mechanisms," said Thomas Shannon. "When a rotor comes off a helicopter, it crashes. When a supreme leader disappears from an authoritarian regime, the authoritarian regime flounders. It does not have the direction it requires. And I think that is what we're seeing at this moment."

Cuban officials have not released details of Mr. Castro's condition. Mr. Castro said in an earlier statement that information about his health must be guarded as a state secret, due to what he described as the threat posed by the United States.