The group issued a two-paragraph declaration denouncing the war in Iraq and condemning U.S. "harassment" of Cuba, which it calls a "pretext for invasion."
Mexican sociologist Pablo Gonzalez announced the declaration Thursday at a May Day celebration in Havana, Reuters news agency reported.
It was also signed by Latin American Nobel laureates Gabriel Garcia Marquez, Rigoberta Menchu, Aldolfo Perez Esquivel and South African writer Nadine Gordimer, also a Nobel prize winner.
The two-paragraph declaration is titled: "To the Conscience of the World."
"A single power is inflicting grave damage to the norms of understanding, debate and mediation among countries," the declaration says, referring to the United States and the war in Iraq.
"At this very moment, a strong campaign of destabilization against a Latin American nation has been unleashed. The harassment against Cuba could serve as a pretext for an invasion."
Mr. Castro's government has come under unprecedented international criticism from friends and foes after sentencing 75 dissidents to prison terms of up to 28 years last month and executing three men who hijacked a ferry in a failed attempt to reach the United States.
Havana has said the crackdown was in response to a U.S. plot to topple the Castro government after more than four decades of failed efforts to do so.
Mr. Belafonte has emerged lately as one of Hollywood's most fervent critics of the Bush administration by attacking its two most senior black officials.
He likened Mr. Powell to a "house slave" who curries favor in the conservative Bush administration "to come into the house of the master."
He has also criticized National Security Adviser Condoleezza Rice for working for President Bush.
His defense of Mr. Castro's regime, along with others who signed the declaration, comes at a time when Cuba's government is being criticized by foreign writers and artists.
Portuguese Nobel Prize-winning novelist Jose Saramago, a longtime supporter of Mr. Castro, wrote last month that, "from now on, Cuba can follow its own course, and leave me out," saying Cuba had cheated his illusions.
At the Thursday rally, Mr. Castro told critics, particularly on the left, that their words could be used to justify a U.S. invasion.
The intellectuals who signed the declaration defending Cuba apparently agree, though they did not specifically express support for Mr. Castro's policies.
The declaration concludes with a call to governments and others to "uphold the universal principles of national sovereignty, respect for territorial integrity and self-determination, essential to just and peaceful co-existence among nations."
Mr. Gonzalez did not say who originated the declaration but that it would continue to be circulated among cultural figures around the world.
While Latin America's revered left-wing intellectuals are abandoning Mr. Castro in horror at the recent crackdown on dissidents, Mr. Garcia Marquez continues to stand by the Cuban leader, an old friend.
The 1982 Nobel Prize-winning author, whose novel "Autumn of the Patriarch" has been acclaimed as the classic account of the Caribbean strongman, refuses to join the likes of Mexican novelist Carlos Fuentes and Uruguayan writer Eduardo Galeano in condemning Mr. Castro.
The Colombian writer defended himself in Tuesday's edition of the daily newspaper El Tiempo after U.S. feminist writer Susan Sontag told reporters that it was "unpardonable" for him not to have spoken out over the recent Cuban crackdown.
"I don't answer unnecessary and provocative questions," said the author, whose sympathies for the Cuban revolution go back decades.
Moral support from such respected figures as Mr. Garcia Marquez is highly valued by a Cuban government whose material resources have dwindled since the Soviet collapse.
"I myself could not calculate the number of prisoners, dissidents and conspirators that I have helped, in absolute silence, to emigrate from Cuba over no less than 20 years," Mr. Garcia Marquez, 76, said in his defense.
"As to the death penalty, I don't have anything to add to what I have said in private and publicly for as long as I can remember: I'm against it in any place, for any reason, in any circumstances," said Mr. Garcia Marquez who lives in Mexico and Los Angeles.
Mr. Castro in 2002 wrote a glowing review of Mr. Garcia Marquez's recently published memoirs.
"In my next reincarnation, I would like to be a writer, and, on top of that, I'd like to be one like Gabriel Garcia Marquez," the communist leader wrote in the Colombian magazine Cambio. [End]
`NO SECRET' ''It is no secret to anyone that Fidel Castro hands over some political prisoners to his courtesans once in a while,'' Vargas Llosa said. ``That is how [García Márquez] keeps his conscience clean. To me it sounds more like repugnant cynicism.'' Vargas Llosa challenged García Márquez to ''intellectually'' explain his support of Castro, but added: ``I doubt very much that he will.'' García Márquez recently condemned the death penalty ''anywhere and for any reason,'' in reply to American writer Susan Sontag, who said she was troubled that the writer had not condemned recent executions in Cuba.***