CARACAS (AFP) - Leftist Venezuelan President Hugo Chavez admitted a relapse of his cancer late Saturday and designated vice president Nicolas Maduro as his heir apparent in case “something happened” to him. Speaking on national television, an emotional Chavez said a return of cancer cells was detected during his most recent visit to Cuba for medical examination, and he will return to the communist-ruled island as early as Sunday for another round of surgery. “During this thorough examination, they again detected some malignant cells in the same area as before,” Chavez said. He did not offer details, but his cancer was first detected in the pelvic area.

Neither the Venezuelan leader, nor his Cuban doctors have ever disclosed what kind of cancer that was.

He admitted he was suffering “somewhat strong” pain and was taking tranquilizers as part of preparation for his upcoming surgery.

Chavez acknowledged that his Cuban medical team had conveyed to him a sense of urgency about the operation, which he said was now “absolutely necessary.”

“The doctor recommended that I undergo surgery yesterday (Friday) at the latest, or this weekend,” he noted. “But I did not agree and came back home.”

Chavez returned from Havana on Friday after a 10-day stay in Cuba. He had not been seen in public for three weeks.

The Venezuelan leader also said that in the event “something happened” and he were incapacitated, vice president Nicolas Maduro would step in and assume control of the government for the rest of the 2013-2019 term, as required by the constitution.

But in what appeared like a presentation of his final will, the president also indicated he would like Maduro to take over the reins of power in a post-Chavez period, urging Venezuelans to vote for him in the next presidential election.

“You choose Maduro as president of the republic,” said Chavez told the nation. “I am asking you this from all my heart.”

Maduro, who has been serving as Venezuela’s foreign minister for the past six years, was appointed vice president in the wake of the October presidential elections. He has held both portfolios since.

Maduro, a former bus driver who began his political career in the labor movement, belongs to the moderated wing of the Chavez entourage. The more radical wing is led by Diosdado Cabello, who, along with Chavez, took part in a failed 1992 military coup, and now presides over the National Assembly.

Firebrand leader Chavez made his latest announcement despite frequent assurances on the campaign trail before his re-election in October that he had been cured of cancer.

Under the Venezuelan constitution, if the new president is incapacitated before inauguration, which is scheduled for January 10, new elections must be called in 30 days. The parliamentary speaker must then take charge until a new president is elected.

But if the incapacitation or death occur after the inauguration but in the first four years of the term, the vice president takes over and governs until an early election determines a new leader.

Recurring bouts of the disease have dogged Chavez’s presidency for the past couple of years, requiring him to spend weeks at a time being treated in Cuba.

He had a cancerous tumor removed from near his pelvic area last year.

The Venezuelan leader, 58, has repeatedly claimed to have beaten the cancer that was diagnosed in 2011 and shrugged off his illness to see off a unified opposition and secure another six-year term on October 7.

In Cuba last week, the official newspaper Granma explained that Chavez’s treatment consisted of oxygenation.

The American Cancer Society says there is no evidence that this oxygen treatment - in which a patient gets inside a pressurized chamber and breathes pure oxygen for an hour - works against cancer.

But the society says it can serve as treatment for ailments stemming from radiation treatment.

Chavez, who has been in power since 1999 and gained global prominence as an anti-American firebrand, appeared weak and subdued during the presidential campaign, but still managed to win another term that extends to 2019.

Prior to Saturday’s surprise announcement, he had last been seen in public on November 15, and two weeks later he went to Cuba for treatment.

Over the past year and a half, Chavez has missed practically every regional meeting he was to have attended, such as the Summit of the Americas in Colombia, the Mercosur summit in Brazil and last month’s Ibero-American summit in Cadiz, Spain.