* Doctors found malignant cells in his pelvic area
* Operation due to take place in Havana within days
* Vice President Maduro tapped as possible successor
By Daniel Wallis and Brian Ellsworth
CARACAS, Dec 9 (Reuters) - Venezuela’s Hugo Chavez returns to Cuba on Sunday for another operation after doctors found a recurrence of his cancer, and the president named a successor for the first time in a sign his illness could force him to step aside.
Supporters prepared to gather in city squares across the South American country, shocked and saddened by the news from the 58-year-old socialist leader, who made the announcement in a late-night broadcast on Saturday from the presidential palace.
In the clearest sign yet that Chavez’s health problems could spell an end to his 14 years at the helm of the OPEC nation, he said supporters should vote for Vice President Nicolas Maduro if a new election had to be held.
“It is absolutely necessary, absolutely essential, that I undergo a new surgical intervention,” the president said in his speech, during which he was flanked by ministers.
“With God’s will, like on the previous occasions, we will come out of this victorious. I have complete faith in that.”
An unruly transition from Chavez’s highly centralized rule could raise the specter of political instability in the country that holds the world’s largest crude oil reserves.
The president’s allies lack the charisma that has made him one of the world’s most recognizable leaders - and most fierce critics of Washington - and may struggle to control his unruly coalition of military leaders and leftist activists.
Speculation about Chavez’s health had grown during a three-week absence from public view that culminated in his latest trip for medical tests in Cuba - where he has undergone three cancer operations since June 2011.
He returned to Venezuela on Friday after those tests, and is due to have the operation in Cuba in the next few days.
He said he had rejected the advice of his medical team to have the surgery sooner, on Friday or this weekend, telling them he needed to fly back to Venezuela to seek the permission of lawmakers to return for the operation.
“I decided to come, making an additional effort, in truth, because the pain is not insignificant,” Chavez said.
‘A COMPLETE REVOLUTIONARY’
The president’s return to Cuba looks sure to mark the start of another lengthy period of silence from government officials, combined with furious rumors over what political changes might be in store and what Chavez’s actual condition is. He has never disclosed what type of cancer is suffering from.
The evident shock on the faces of Cabinet ministers during Saturday’s broadcast signaled that uncertainty over the country’s future reigns, even in the top echelons of power.
Chavez has been receiving treatment at Havana’s Cimeq hospital as a guest of his close friend and political mentor, former Cuban leader Fidel Castro. He is guaranteed tight security and privacy on the communist-led Caribbean island.
The usually loquacious Venezuelan leader had sharply cut back his appearances since winning the Oct. 7 election, saying the campaign and radiation therapy had left him exhausted.
Under the constitution, an election would have to be held within 30 days if Chavez were to leave office in the first four years of his next six-year term, which is due to begin on Jan. 10.
For the first time, in a rare admission he might not be able to govern for as long as he hopes, he singled out Maduro - a 50-year-old former bus driver and union leader - as his candidate.
“He is a complete revolutionary, a man of great experience despite his youth, with great dedication and capacity for work,” Chavez said. “In a scenario where they were obliged to hold a new presidential election, you should choose Nicolas Maduro.”
Maduro’s trade union background appeals to Chavez’s working-class supporters, while his previous role as foreign minister provided opportunities for networking abroad.
He may win less support from the military wing of the Socialist Party, which controls many top government posts.
Venezuela’s widely traded bonds are likely to soar when markets open on Monday on expectations that Chavez’s renewed illness will pave the way for a more market-friendly government. Its bonds have been among the most profitable of any emerging market paper this year, largely due to Chavez’s weak health.
His possible departure could mark the end of an era of socialist governments in Latin America and anti-U.S. sentiment that Chavez helped set in motion more than a decade ago, and leave global leftists without one of their most acerbic voices.
The opposition could find itself in its best position to oust his administration since Chavez took power in 1999. Many voters have ignored the failings of Chavez’s government because of their intense emotional connection to him.