By Brian Ellsworth and Andrew Cawthorne
CARACAS (Reuters) - President Hugo Chavez broke a week-long silence on Monday to deny he had left Venezuela rudderless during his cancer treatment in Cuba and to promise a resounding re-election win in October.
"I'm governing - fulfilling my duties as head of state - but in this unique situation which I will be out of in the next few days, and then soon I will be back there," Chavez told state TV in a brief phone call, his voice sounding firm and energetic.
Chavez's normally ubiquitous media presence had slowed to a trickle of Tweets in recent days. He had not made any live contact with state media in the week since a public appearance last Monday before leaving for Cuba to receive treatment.
That had fanned criticism that he was no longer properly running the country and spurred unprecedented talk of a successor to the former soldier, who during 13 years in power has avoided cultivating a protégé who could replace him.
But Chavez insisted he was still in charge of government and would be back home soon to start mulling his re-election campaign.
"The opposition are never going to win any elections in Venezuela, ever again, we are going to give them a resounding knockout," he said.
"I am governing with my full faculties."
Chavez's health is treated as a state secret.
He has had three operations since last June, including one that removed a baseball-sized tumor. But government leaders have refused to divulge details about his condition.
He is supposed to have completed the last of five radiotherapy sessions, but the unusual silence had fanned speculation his condition was getting worse, possibly fatal.
TRANSITION TALK GROWS
The recent creation of a Council of State, charged with advising the president on policy issues, has been interpreted by analysts and some opposition activists as a transition agency that could ease the way toward a post-Chavez Venezuela.
Party leaders deny this, insisting he is their only candidate and assuring voters he will sweep opposition rival Henrique Capriles in the October 7 vote.
"It is not a transition (committee) and there will be no transition," said Vice President Elias Jaua at the weekend in a ceremony filled with Chavez supporters clad in signature red shirts chanting party slogans.
"There will be elections, re-election and a new term for Hugo Chavez."
Allies seen as potential replacements for him if he cannot run in the October 7 vote include Jaua, Foreign Minister Nicolas Maduro, and National Assembly President Diosdado Cabello.
Chavez's two daughters, who have no political experience but frequently appear with him in public, are seen as potential stand-ins who could command respect from supporters and allies.
"There is no way to know the likelihood of any given scenario without serious information about Chavez's health," said local pollster and analyst Luis Vicente Leon via Twitter.
"But one thing is clear: Chavez will be the candidate, dead or alive. Even if Chavez is physically absent, the campaign will be full of his symbols, photos, messages and missions."
Chavez has spent most of the last six weeks in Havana, and only been seen once live in public since mid-April.
He ended a short address a week ago choking on his words, with tears in his eyes, in sharp contrast to his triumphant speech to Congress in January that stretched for nine hours.
His recent Twitter comments have been limited to greetings to allies and promises of state funding for arcane projects ranging from fixing broken elevators to boosting sugar cane production.
One source close to the government said Chavez's health has deteriorated considerably with the radiotherapy. He has been in intense pain and is unable to walk, requiring him to use a wheelchair, the source told Reuters.
"There is great anxiety over what is coming," the source said.
Financial markets have reacted positively to speculation over Chavez's illness, with the country's bonds rallying broadly on the possibility of a more market-friendly government.
Chavez's oil-financed social welfare crusade has made him immensely popular among the country's poor, who have handed him repeated ballot box victories since he first won office in 1998.
Opposition leaders, who have avoided directly commenting on his illness, describe him as a doctrinaire autocrat whose steady expansion of the state has weakened the economy and left Venezuelans dependent on state handouts.
(Additional reporting by Eyanir Chinea, Mario Naranjo and Diego Ore; Editing by Cynthia Osterman)