HAVANA (Reuters) - Cuban revolutionary leader Fidel Castro took his warning of impending nuclear war to Cuba’s Foreign Ministry on Friday, where he explained the reasons for his dire prediction in his fifth public appearance in 10 days.

Former Cuban leader Fidel Castro (2nd L) stands with trainers of Havana's National Aquarium during a visit July 15, 2010. Castro has been seen only in occasional photographs and videos since he underwent emergency intestinal surgery in July 2006 and ceded power provisionally to his younger brother, Raul Castro. He resigned in February 2008 and Raul Castro was officially elected president by the National Assembly. REUTERS/Revolution Studios

Castro’s sudden re-emergence after four years in seclusion for health reasons has raised questions about his intentions, but his message has been consistent -- a devastating war is at hand if the United States, in alliance with Israel, tries to enforce international sanctions against Iran for its nuclear activities.

He also has predicted the United States will attack North Korea.

“The United States finds itself now in an unsolvable dilemma (in the Middle East). It cannot get out, nor can it stay,” Castro told 115 ambassadors, who listened with rapt attention.

“It won’t get out of that situation through diplomacy, but through the power of its arms,” he said, pointing his finger in the air and pontificating at length as in the old days.

Castro, 83, spoke for more than an hour as he sat in front of the ambassadors. He looked fit, relaxed and fully in charge as he took questions and read numerous news reports to back up his position.

He said he had partially recovered from the “sudden and grave situation of health” that forced him from power.

Castro disappeared from public view following emergency intestinal surgery in July 2006 and ceded power to his younger brother, now President Raul Castro.

He resurfaced on July 7 at a scientific research center in Havana and has since made several appearances in person and in a videotaped television interview.

Theories abound about why the man who ruled Cuba for 49 years after taking power in a 1959 revolution has returned to public view. He has said his only interest is in warning the world of the coming conflict.

His reappearance has coincided with Cuba’s biggest release of political prisoners since 1998, in a deal cut with the Catholic Church, and intentional or not, has drawn away from it.

The church announced on July 7 that 52 political prisoners, or about a third of the island’s jailed dissidents, would be freed over the next few months. The releases began on Monday.

Wide-ranging speculation includes theories that Castro is sending a message of stability at a time of uncertainty about Cuba’s future, that he felt his warning of war was being ignored, or that he simply wanted to return to the limelight.

The Cuban government has said nothing except for the reports of his visits in state-run media, which on Friday said Foreign Ministry employees and people from the surrounding neighborhood sent him off with a “prolonged ovation and emotional (shouts of) ‘Viva.’”