Updated

President Hugo Chavez said for the first time Wednesday that he expects to undergo chemotherapy or radiation treatment, providing the clearest picture yet of his prognosis three weeks after undergoing surgery that removed a baseball-sized tumor.

Chavez provided new details about both his June 20 surgery in Cuba and his post-operation treatment, suggesting he anticipates a long road to recovery from cancer that could include physically taxing treatments in the coming months.

He said in a phone call to state television that he is now starting a second phase of treatment and expects a third phase "that could be a bit hard." He said the purpose would be to "armor the body against new malignant cells of this type."

"It would most likely require the use of methods that are known ... depending on the evolution and these follow-up diagnoses, but it could be radiation therapy or chemotherapy," Chavez told state television in a phone call.

The president said such treatment would be to "attack hard, with cavalry, any possibility, anything latent that might be there." He did not say how soon such treatment might begin.

Chavez still did not reveal what sort of cancer is involved.

He said the operation lasted about six hours and removed a tumor that was "encapsulated."

"I had a big, big tumor," Chavez said. "When I saw that image, I said, 'My God, it's a baseball."'

Since his return to Caracas on July 4, the 56-year-old leader has limited the length of his televised appearances, saying he is under strict orders from his doctors.

Chavez said Wednesday that he is recovering well, and suggested some of his foes hope he does not.

"I have cancer, but not in the way some would want," Chavez said.

He earlier said the operation was in his pelvic region, but denied Wednesday that his colon had been cut during the surgery.

That implies Chavez could have suffered bladder, kidney, prostate or rectal cancer, although doctors consider the rectum part of the colon, said Dr. Michael Pishvaian, a cancer specialist at Georgetown University's Lombardi Comprehensive Cancer Center who was not involved in the Venezuelan leader's treatment.

Another possibility is a sarcoma, a soft-tissue cancer that can occur anywhere in the body and that often is encapsulated, or contained within a pouch of tissue.

Radiation is given to kill any remaining tumor at the original site. Chemotherapy is to treat any tumor that has spread or to kill stray cancerous cells that might seed a new tumor.

"He's essentially probably getting these treatments in the hopes of preventing any recurrence of the disease," Pishvaian said. "The idea is to try to eradicate any microscopic disease that might be present."

Radiation typically involves daily treatments for four to six weeks. Chemotherapy is given periodically for about six months, depending on the regimen and how well the patient tolerates treatment, Pishvaian said.

In most cases in which a tumor is removed, patients must go through a recovery period to be able to tolerate radiation treatment or chemotherapy, said Dr. Javier Cebrian, chief of surgery at Unveristy Hospital of Caracas.

Cebrian, who is not involved in treating Chavez, said various characteristics of the tissues affected by a tumor are more important factors than a tumor's size. He said each patient reacts differently to chemotherapy and radiation, and may be able to "lead a normal life and carry out his or her work."

Chavez said his first phase of post-surgery treatment has turned out well, "thanks to God and to medical science, and to this body, which seems tougher than what I myself believed."

Chavez also said, however, that he is constantly observed by a doctor and a nurse who accompany him even at night, and that he undergoes regular evaluations because "the threat of ... expansion, outbreak is always latent."

Foreign Minister Nicolas Maduro said earlier this month that the operation to extract the tumor was performed in the same area as another surgery nine days earlier to remove a pelvic abscess.

Maduro said specialists confirmed after the operation that "the entire abscessed tumor was able to be removed, all of his organs were checked, that they are in perfect shape."

Chavez said Wednesday that he has achieved a "recovery of vital signs, well, recovery of weight, recovery of all blood levels," though he said he was still about 31 pounds (14 kilograms) below his earlier weight.

"I'm now getting close to my weight of 85 (kilograms)," or 187 pounds, Chavez said. "I was at more than 100 kilos (220 pounds) ... I looked like a battle tank."

Chavez, who is up for re-election in late 2012, has been actively posting messages on Twitter and has appeared on television in the past several days leading a Cabinet meeting, doing stretching exercises with aides and attending Mass.

Chavez, a former army paratroop commander, has said his rehabilitation regime requires discipline, including waking up at 5 a.m. That is a significant change for a president known for speaking regularly late into the night and summoning his ministers at all hours.

Chavez said cancer has led him to reflect about what he called "fundamental errors" in his lifestyle, such as drinking "40 cups of coffee in one day," carrying three cellphones, eating whatever was available and "not sleeping, not letting my ministers sleep."

He also acknowledged it has been a serious mistake to be habitually "talking too much."

Chavez has said his doctors have advised him to limit the length of his televised talks, which in the past could run as long as seven or eight hours.

"I'm on that, slowing down the horses I lead, but learning. I'm learning. I have to learn to delegate more," Chavez said.

The president attended Mass on Tuesday night at Caracas' Military Academy, joining friends and aides in praying for his recovery.

Chavez also said in separate remarks to state television Tuesday that he intends to remain in the presidency and accelerate his drive for socialism in Venezuela.