Castro, 80, has attended the annual May Day march for decades, but there was no official word whether the leader would be well enough to make it this year.
The Communist Party newspaper Granma declared that marchers at the Tuesday event in Havana's Plaza of the Revolution will be "united and strong with the revolution and the party, with Fidel and Raul" Castro.
Smaller marches will be held simultaneously in other cities around the island, with the government expecting several million of the nation's 11 million people to participate.
Marchers also will protest the recent decision to free on bond anti-communist militantpending his trial on U.S. immigration charges.
Cubans are enraged by the re-emergence of Posada, one of Castro's oldest enemies, reports CBS News chief foreign correspondent Lara Logan. To Cubans, Posada is their Osama Bin Laden, accused of blowing up a Cuban jetliner in 1976 with 73 people on board, and a string of hotel bombings.
Watching the former CIA agent and Cuban exile walk free was a sight most Cubans didn't want to see, adds Logan.
Fidel Castro has not appeared in public in the nine months since announcing he underwent emergency intestinal surgery and temporarily ceded his functions to his 75-year-old brother Raul, the defense minister. He has appeared only occasionally in government photographs and videos, appearing stronger and more robust in more recent images.
He met separately in recent weeks with Colombian writer and Nobel laureate Gabriel Garcia Marquez and a top Chinese Communist Party leader and has penned three editorials.
Cuban officials have given increasingly upbeat reports about Castro's health, but have declined to speculate about whether he will appear Tuesday.
Some Castro loyalists remained hopeful.
"I pray that he appears," said retiree Manuel Otero. "It would be satisfying to know that he has overcome (his illness) and is with us in the struggle."
"The whole world misses him," said public works employee Rose Elena Perez.