ARACAS: Venezuelan President Hugo Chavez was set to leave for Cuba early Monday to undergo new cancer surgery that the leftist leader admitted was urgently needed to fight the deadly disease.

It will be the fourth time the firebrand anti-American populist, re-elected only last October, has undergone surgery since being diagnosed last year.

But this time there was a more ominous tone as Chavez, whose country sits atop the world’s largest proven oil reserves, spoke for the first time of the idea of succession, naming Foreign Minister and Vice President Nicolas Maduro as his favored heir apparent.

Chavez disclosed his upcoming surgery on Saturday night (Sunday in Manila), shortly after returning from 10 days of treatment in Cuba.

The announcement shocked people who have come to know him as an indefatigable and garrulous man who was a fixture of their everyday life.

Chavez, 58, had said he was cancer-free after being diagnosed last year and treated. But he dramatically announced on Saturday that malignant cells had returned and that he needs more surgery.

Treatment is “absolutely necessary,” Chavez said in a bombshell statement on state television in which he admitted he may have to give up the presidency and that Maduro was his chosen successor—a move analysts saw as the first step of a political transition.

The designation of an heir apparent in the event that “something happened” to him underlined the seriousness of Chavez’s condition, which he said was causing his strong pain and required him to take tranquilizers.

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

He returned on Friday after his latest stay in Cuba, during which his medical team stressed a sense of urgency about the looming operation, his fourth since mid-2011.

In what appeared like a presentation of his final will, the once-omnipresent leader, who had not been seen in public for three weeks, urged Venezuelans to vote for Maduro in the next presidential poll should he become incapacitated.

“Choose Maduro as president of the republic,” Chavez said. “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 October’s presidential poll. He has since held both portfolios.The 49-year-old former bus driver who began his political career in the labor movement belongs to the more moderate wing of the Chavez entourage.

Paving the way for his departure, the National Assembly on Sunday granted Chavez permission to travel to Cuba and, in another possible indication of the seriousness of the matter, leave the country for an indefinite amount of time.