Mr. Castro was noticeably absent Saturday, as a massive military parade in celebration of his 80th birthday marched down the streets of Havana.
The event also marked the 50th anniversary of Mr. Castro's landing in Cuba to launch a revolution.
President Castro's younger brother, Raul, led the event, and addressed the assembled crowd, saying that Cuba is willing to negotiate its differences with the United States, as long as the discussion is based on equality and mutual respect.
The United States says it would move to re-establish diplomatic ties with Havana and drop the long-standing U.S. trade embargo against Cuba if and when genuine democracy takes hold on the island.
Huge crowds of flag-waving Cubans cheered the procession of tanks and soldiers. Several guests of honor attended the event, including Bolivian President Evo Morales.
Organizers had rescheduled the five-day birthday celebration from August after Mr. Castro underwent intestinal surgery and handed over power to his brother, Raul.
Details of the Cuban President's health are a state secret, and he has not made a public appearance since July.
The Cuban government has periodically released pictures and videos of Mr. Castro to reassure Cubans that he is still alive.