CARACAS, Venezuela (AP) -- President Hugo Chavez announced Tuesday that doctors in Cuba found a new lesion in the same place where a cancerous tumor was removed last year and said he will shortly return to the island to have it surgically removed.
He told Venezuelans he did not know if the lesion is malignant but that the probability is high, adding that they should not expect to see him in coming weeks as he will likely need localized radiation therapy.
"I'm not going to be able to continue with the same rhythm," Chavez told state TV via telephone Tuesday night, adding that he would need to "rethink my personal agenda and take care of myself, confront what must be confronted."
The announcement thrust Venezuelan politics into new uncertainty because the socialist leader is seeking re-election this year, hoping to extend his more than 13 years in power with a new six-year term.
Initialy announcing the lesion in an afternoon state TV appearance from his home state of Barinas, Chavez said the lesion was about "two centimeters (less than one inch) in diameter, very clearly visible."
He said it would be removed by the same surgeons who excised a tumor from his pelvic region last June, and expected the new operation would be less complicated.
Chavez, 57, did not say when he would depart for Cuba. He said he would attend to government business Wednesday, including signing papers, meeting with the Cabinet and armed forces leaders.
He said he would head for Havana "without haste. All in good time."
A leading Colombian oncologist, Dr. Carlos Castro, said that if Chavez undergoes radiation therapy that typically means a minimum of 10 daily sessions, which means Chavez would need to name a temporary replacement while undergoing treatment.
From July to September, Chavez received four rounds of chemotherapy, both in Cuba and in Venezuela, and subsequently said tests showed he was cancer-free.
On Tuesday, Chavez denied rumors that the cancer had spread aggressively.
"I completely deny what's going around that I have metastasis in the liver or I don't know where, that the cancer has spread all over my body and that I'm already dying," he said.
He has never specified the cancer's exact nature or location, and critics have repeatedly accused Chavez of a lack of transparency.
Analyst Cynthia Arnson of the Woodrow Wilson International Center in Washington said Tuesday's announcement seriously complicates Chavez's prospects for re-election on Oct. 7.
"It's now clear that Chavez's cancer is far from cured. Chavez's illness -- his ability to campaign as well as to govern -- is a major factor in the race. It erodes the aura of invincibility as well as inevitability that Chavez has always tried to create," she said.
The governing party will also be vexed as it lacks an alternative with Chavez's charisma and popular following, Arnson said. She predicted "a tight race (will get) even tighter" against opposition candidate Henrique Capriles, a 39-year-old state governor.
He said rumors, including that the cancer has been spreading, prompted him to go public. He had been out of public sight since Friday, not announcing his trip to Cuba.
His government's handling of unconfirmed reports that he spent the weekend there undergoing medical tests turned out to be ham-fisted. On Monday, repeated attempts by The Associated Press to confirm the reports went unanswered, and Communications Minister Andres Izarra vehemently denied them online.
"Regarding the rumors, dirty war from the gutter," Izarra tweeted.
Also Monday, an employee of the Venezuela Embassy in Havana said there was no indication Chavez had gone to Cuba or planned to do so. The person did say that some members of the presidential family were in Cuba but had already left. The employee spoke on condition of anonymity, lacking authorization to discuss the matter publicly.
Chavez, whose approval ratings have topped 50 percent in recent polls, has in recent weeks recovered the hair he shaved off during chemotherapy and appeared vigorous, albeit puffy around the face and neck. He had returned to a full schedule of activities including marathon television appearances.
"I am in good physical shape to confront this new battle," Chavez said on Tuesday afternoon.
He later choked up, reflecting on mortality in the phone call.
"I ask for life," he said. "I want to live with you and fight with you until the last moment of this life that God gave me."
He called on his backers to "accelerate the (electoral) battle."
Doctors consulted by the AP said it was difficult to assess Chavez's prognosis.
But Dr. Javier Cebrian, a colorectal specialist and chief surgeon at University Hospital in Caracas, said news that the lesion was in the very place the initial tumor was removed was not good.
"A local recurrence is a bad symptom because it means the illness is growing again," he said.
"It's an ominous sign," said Dr. Michael Pishvaian, a Georgetown University oncologist. He said doctors often use the term lesion to refer to a new tumor, which appears to fit Chavez's description.
He said such a reappearance, particularly when a patient has undergone surgery then chemotherapy, suggests cancerous cells have resisted the treatments.
Many Venezuelans have been impressed by Chavez's fortitude.
"It's already established that Chavez is a superman because he was sick and he didn't delegate to anyone," said Luis Montilla, a 51-year-old lawyer.
Capriles' campaign coordinator, Armando Briquet, said he and his team wish Chavez "a complete recovery" and "a long life although we have always been critical about the lack of real information about the president's health."
Capriles claims Chavez has exploited his lengthy rule to balance the scales against a fair election, taking advantage of government money and slanted coverage in state media.
He is a strident critic of Chavez's expropriations of hundreds of businesses, apartment buildings and farms over the past decade.
The government's generous spending has made Chavez a hero to many of his supporters, which make up a large segment of Venezuela's poor.
Opponents say Chavez has done nothing to combat Venezuela's rampant violent crime and blame him for 26 percent inflation. His opponents also criticize the former paratroop commander for his strident anti-U.S. rhetoric and defense of Iran and its nuclear program.
The U.S. Embassy in Caracas has been without an ambassador since July 2010.
Associated Press writers Vivian Sequera in Bogota, Colombia, Ian James in New York and Andrea Rodriguez in Havana contributed to this report.