HAVANA - A lively and healthy-looking Fidel Castro appealed to President Barack Obama to stave off global nuclear war in an emphatic address to parliament Saturday that marked his first official government appearance since emergency surgery four years ago.

Castro, who turns 84 in a week, wore olive-green fatigues devoid of any military insignia and arrived on the arm of a subordinate who steadied him as he walked. The approximately 600 lawmakers present sprang to their feet and applauded, as the gray-bearded revolutionary stepped to a podium that had been set up for him, grinning broadly and waving.

"Fidel, Fidel, Fidel!" chanted the members of parliament. "Long live Fidel!"

Castro has been warning in written opinion columns for months that the U.S. and Israel will launch a nuclear attack on Iran and that Washington could also target North Korea - predicting Armageddon-like devastation and fighting he expected to have already begun by now.

"Eight weeks ago, I thought that the imminent danger of war didn't have a possible solution. So dramatic was the problem that I didn't see another way out," Castro told the legislature. "I am sure that it won't be like that and, instead ... one man will make the decision alone, the president of the United States."

He added of Obama, "Surely with his multiple worries, he hasn't realized this yet, but his advisers have."

Castro didn't mention domestic Cuban politics or the foundering economy - instead sticking to the threat of war, the issue for which he convened Saturday's special session of parliament.

Still, his attendance, along with a slew of recent public appearances following a nearly four-year absence from public view, is sure to raise more questions about how much of a leadership role Castro is ready to reassume.

Is he itching to retake his position as Cuba's "maximum leader" - or simply well enough to warn lawmakers in person that the end of the world could be near?

Castro's speech lasted barely 11 minutes - possibly a record for the man who became famous for his hourslong discourses during 49 years in power - and was largely devoid of his usual America bashing. He referred to the United States as "the empire" only a few times - though he did say that if Obama didn't intervene he would "be ordering the instantaneous death ... of hundreds of millions of people, among them an incalculable number of inhabitants of his own homeland."

In Washington, there was no immediate response from the White House.

Castro moved to a seat after his speech, and was briefly approached by his wife, Delia Soto del Valle. The couple rarely appeared in public together in the past, but Soto has been seen with Castro more frequently of late.

It was Castro's first appearance in parliament or at a government act since shortly before a health crisis in July 2006 that forced him to cede power to his younger brother Raul - first temporarily, then permanently. He underwent emergency intestinal surgery prompted by an illness whose exact nature has been kept a state secret, and spent years recovering in an undisclosed location.

Lawmakers have always left an empty chair to the right of Raul. It was in its usual spot Saturday - but Fidel did not sit in it.

Instead, he sat next to Parliament head Ricardo Alarcon. The two consulted and cracked jokes during the assembly's one-hour-and-40-minute session. Raul Castro sat nearby, though on another part of the stage, listening intensely to the proceedings and taking notes when Fidel delivered his speech.

While it was the first time the brothers have appeared together publicly since Fidel fell ill, neither made any effort to approach the other, and they never even seemed to make eye contact.

Lawmakers followed Fidel Castro's speech with enthusiastic remarks about how fully recovered and healthy he appeared. They also commented on the possibility of war.

Asked by one parliamentarian if Obama would be capable of starting a nuclear conflict, Castro replied, "No, not if we persuade him not to."

There was an uncomfortable pause as the room waited for him to continue in his trademark long-winded style. Instead, Castro patted his hand on the desk for emphasis, then fell silent, drawing surprised applause from the crowd.

Even before Castro appeared before parliament Saturday, lawmakers and other top leaders had joined state media in calling him "commander in chief," a title he had largely shunned since relinquishing power.

"Fidel attracts more people. There's nobody better than him," said Pedro Gonzalez, a 90-year-old retiree who watched the session of parliament on a nationwide broadcast. "Look how well he's recuperated. It's incredible. Fidel makes us feel better."

Castro's message did not go over well with everyone, however. Maite Delgado, 50, started watching Castro on TV - then turned away.

"This is surreal. It seems like something that's detached from reality," she said. "I'm looking for an explanation to Fidel's warning about war and I can't find one. I can't find any explanation for what he's talking about and ask myself, 'How is it possible that he doesn't speak about all of Cuba's internal problems?"'

A sudden media blitz by Castro has seen him make near-daily appearances around Havana in recent weeks. He has addressed groups of Cuban intellectuals and Communist Youth meetings, and even made a trip to the Havana aquarium for a dolphin show.

Alarcon abruptly called Saturday's session to an end, saying it was not the only "revolutionary duty" Castro had scheduled for the day. Castro responded rather sheepishly that, these days, he has "more time than I know what to do with."

Associated Press Writer Anne-Marie Garcia contributed to this report.