Cuban leader Fidel Castro called into Venezuelan President Hugo Chavez's radio talk show, saying he felt "more energetic" and was enjoying his convalescence in his first live comments since falling ill seven months ago.

"I'm gaining ground. I feel more energetic, stronger and have more time to study. I've become a student again," he told Chavez over the phone Tuesday in a soft but steady voice.

"I can't promise that I'll go over there soon," Castro said, but added, "I feel good and I'm happy."

Until Tuesday, Castro only had been heard in pre-taped comments on videos released by the Cuban government, which quelled speculation that he was deathly ill but failed to give an immediate sense of his health.

His words to Chavez were spoken slowly — and he appeared to catch on a few words — but he was in good spirits.

"My God! It's Fidel," Chavez said with obvious surprise at the unexpected call and asked his close friend in English, "How are you?"

"Very well," Castro replied in English, prompting a chuckle from Chavez.

"You don't know how happy we are to hear your voice and know that you're well," Chavez said.

During the 30-minute conversation, Castro touched on various topics, including a reference to a plunge in U.S. and Chinese stocks earlier in the day that he said should be a cause for worry for the U.S. government.

The 80-year-old leader transferred control of Cuba's government to his brother Raul, 75, after undergoing intestinal surgery in July and dropped out of public view, fueling speculation about his condition.

Cuba's communist government has kept Castro's condition and exact ailment secret, and Chavez acknowledged that he has become an "emissary" for news of his close friend and ally's health.

Castro thanked Chavez for keeping people informed but complained that his supporters have "the habit, the vice" of expecting daily updates and asked for patience, saying he is not the long orator he once was.

"Totally mute. I can't talk every day. I ask everyone for patience, calm ... the country is marching along, which is what is important," he said.

"And I ask for tranquility also for me so that I can fulfill my new tasks," he said.

The conversation was not aired live in Cuba but, shortly afterward, Cuban state television broke into the regular nightly news program to broadcast the exchange.

In Miami, Alfredo Mesa, spokesman for the Cuban American National Foundation, said Castro is already part of the past and encouraged others to stop following the minute details of his illness.

"We need to stop worrying about Fidel Castro's health and focus more on the people in positions of power today that can bring about change for the Cuban people," Mesa said. "It's no longer about Fidel Castro."

Cuban officials have denied U.S. government reports that Castro suffered from cancer. A Spanish newspaper reported last month that he had diverticular disease, a weakening of the walls of the colon.

The Cuban government has sought to reassure Cubans after Castro ceded power for the first time in 47 years, saying his health is stable and the defense of the island guaranteed. It released a new video on Jan. 30 of Castro looking stronger than in previous images as he met with Chavez.

Chavez ended his conversation with his mentor telling him: "We will win time and win the battle for life."

"Fatherland or death. We will prevail!" the two leaders repeated after each other.