Troops are massing for a huge parade and guests are arriving from around the world to celebrate Fidel Castro's delayed 80th birthday party. The only question is whether the ailing guest of honor himself will appear after four months out of the public eye.

Whether Castro shows up for some of the five days of festivities starting Tuesday will give the Cuban people and the world clues about the leader's health and ability to resume the power he held for 47 years — or at least feed further speculation about it.

Rows of troops in olive green fatigues marched Monday morning across Havana's Plaza of the Revolution to prepare for a big military parade on Saturday honoring Castro and marking the 50th anniversary of the island's Revolutionary Armed Forces.

Just outside the plaza, more than a dozen missile launchers were lined up while military helicopters buzzed and MiG jet fighters zoomed overhead.

If Castro does appear, Cuban authorities will likely celebrate it as a major victory over the leader's enemies. A no-show will likely set off a new round of speculation about his health, his chances for survival and the nation's future.

Details of Castro's ailment have been treated as a state secret and his absence from the public scene has fueled persistent rumors about his health — especially among his enemies in the Cuban exile community in South Florida.

Despite periodic statements by Cuban officials insisting he is recovering nicely, U.S. officials say they are convinced Castro suffers from some kind of inoperable cancer and won't live through 2007.

Castro has been seen by the public only in photos and videos since announcing on July 31 he was temporarily ceding power to his 75-year-old brother, Defense Minister Raul Castro, after his emergency operation for sustained intestinal bleeding.

Although the latest images released in late October showed Castro had regained much of the 41 pounds reportedly lost since he fell ill, he nevertheless appeared pale and fragile.

Senior Cuban officials have declined to speculate on whether Castro will show up at any of the events, while still expressing optimism about his recovery.

"If he considers it appropriate, depending on his rehabilitation program, perhaps he'll decide to go," National Assembly President Ricardo Alarcon said earlier this month.

Colombian writer Gabriel Garcia Marquez, Bolivian President Evo Morales, Mexican actress Maria Rojo, former Ecuadorean President Rodrigo Borja and Argentine ex-soccer star Diego Maradona are among more than 1,300 people organizers say will attend.

Brazilian poet Thiago de Mello, Ecuadorean writer Jorge Enrique Adoum and Nicaraguan politician Tomas Borge arrived over the weekend.

Castro's good friend and political ally Venezuelan President Hugo Chavez won't be able to come; he is up for re-election on Dec. 3. But Chavez has promised to dedicate his electoral victory to Castro.

Birthday celebrations sponsored by the foundation of late Ecuadorean painter Oswaldo Guayasamin begin with a party Tuesday night and include a three-day academic conference, a concert featuring Cuban and Latin American artists and an art exposition.

The festivities were originally scheduled around Castro's actual birthday on Aug. 13. After falling ill, Castro asked to postpone them to coincide with the military anniversary.

Guayasamin, who died in 1999, was a close friend of the Cuban leader. He painted four portraits of Castro over the years and joined him once every decade to celebrate his birthday.