The Venezuelan leader, Hugo Chavez, has admitted in a television address that he had a tumour but had undergone a successful operation in Cuba to extract the cancerous cells and was on the road to full recovery.
Chavez, 56, made his first televised speech to the nation on Thursday, weeks after he was hospitalised in the Cuban capital, Havana, sparking widespread speculation he might be seriously ill.
"They confirmed the existence of a tumourous abscess, with the presence of cancerous cells, which required another operation to extract the tumour completely," he said, standing at a lectern by a Venezuelan flag and a painting of his hero, South American independence leader Simon Bolivar.
"I deeply appreciate the demonstrations of solidarity by Venezuelans and other brotherly people."
Chavez said the medical process was "slow and careful" and that he was determined to "overcome" the health battle.
Comparing his health problem to a previous dark moment - a short-lived 2002 coup against him - Chavez promised he would be back in typically grandiose language.
"I want to talk to you about the rising sun, I think that we have emerged," he said.
Blogger Juan Nagel comments on Chavez's address
The Venezuelan government had earlier said he was recovering from an abcess in the pelvis in Cuba, from where Thursday's speech was broadcast.
Shortly after the speech, Venezuela's vice-president, Elias Jaua, flanked by government ministers, said on state television that the wide-reaching socialist reforms would be "deepened" despite Chavez's ill health.
He insisted Chavez was in "full exercise of authority" from Cuba.
While Rafael Ramirez, the energy minister, said: "Let no one have any doubts - it's Chavez who's in charge here."
And Venezuela's military chief said there is no threat to the country's constitution.
Army chief General Henry Rangel Silva said the military would guarantee constitutional order during Chavez's absence.
Nevertheless, there is huge uncertainty about who could replace Chavez, given the fact that Venezuela's political structures are so closely tied to his persona.
"Chavez is really the man of Venezuela," Al Jazeera's Mariana Sanchez said. "There's really not a figure in the ruling party, or even in the opposition, that will match the charisma that Hugo Chavez has."
Analysts said Chavez's prolonged absence could prompt infighting among his allies ahead of the 2012 elections.
"From the president's speech, it is impossible to deduce if he will or will not be in a physical state and the right mood to go into the 2012 campaign," Luis-Vicente Leon, a local analyst, said.
Eva Golinger, a lawyer and writer in the Venezuelan capital, Caracas, told Al Jazeera there was "no sign" Chavez would not be able to continue as president.
"He gave his speech ... from a very energetic and strong and charismatic position and so it seems as though he's recovering well," she said.
"He is someone who has faced all kinds of difficulties and obstacles, particularly during his presidency, and so it seems as though he is going to pull through this one just fine."
Until Thursday, the official line had been that he was recovering well from an operation to remove a pelvic abscess and would return soon.
Inheriting former Cuban revolutionary leader Fidel Castro's mantle as Washington's main irritant in Latin America, Chavez has become one of the world's most well-known leaders during his 12 years in power.