Venezuelan President Hugo Chavez flew to Cuba late Saturday to begin radiation therapy one month after undergoing surgery that removed a cancerous tumor.

Chavez will be in Cuba at the same time as Pope Benedict XVI, who arrives on the communist-governed island on Monday after a visit to Mexico. But Chavez didn't refer to the pope's upcoming visit to Havana.

The 57-year-old president describes himself as a Christian. He has regularly clashed with Roman Catholic leaders in Venezuela, but during his illness has often publicly expressed faith in God that he will overcome cancer.

Chavez said the radiation treatments are to begin right away on Sunday. He has been recovering from a Feb. 26 surgery in Havana that he said removed a tumor from the same spot in his pelvic region where another tumor was extracted eight months earlier.

"I've decided, on the recommendation of my medical team and also my government political team, to begin ... radiation therapy treatment," Chavez said in a televised meeting with aides Saturday. He described it as a "complement to the surgery that I underwent."

"Yesterday, they took out the last stitches that were left from the operation. Everything's very good. I've been walking much better. ... Without any sort of complication, thanks to God," he said. "And now, a month after the operation, we're ready for radiation therapy, which will last about four, five weeks."

At Caracas' international airport Saturday night, Chavez held the hand of one of his daughters as he walked past soldiers standing at attention.

"I'll be back in a few days," he said. "You should know that radiation therapy is for various days, and after that a break, and after that other days and another break. So I'm going to be going and coming. It's possible that we may do some of the sessions here in Venezuela. We're evaluating it. What's most important, whether its there or here, is the effectiveness of the treatment."

Chavez has not identified the type of cancer nor the precise location where the tumors have been removed.

After he was diagnosed with cancer in Cuba last year, Chavez underwent an initial surgery in June that removed a tumor the size of a baseball.

He then had four rounds of chemotherapy and said tests showed no signs of any cancerous cells. But last month, he announced he was returning to Cuba for surgery to remove a lesion that proved to be malignant. He has described the most recent tumor as measuring about 2 centimeters (0.8 inches).

Chavez had said earlier this month that he would undergo radiation therapy but had not given details about when it would begin or where he would be treated.

Chavez is running for re-election in October and vows that his illness will not get in the way of that political goal.

His rival, opposition leader Henrique Capriles, has criticized Chavez's handling of his cancer, saying that the president should be releasing complete details about the illness.

Chavez defended his decision to return to Cuba rather than undergo radiation treatment at home.

"The opposition is criticizing me because I'm going to Cuba. ... Here we have excellent hospitals, excellent doctors. But well, it was there that they detected my cancer. It was there that they performed an emergency operation on me the first time (in June)," Chavez said at the airport.

He added that even while away, he plans to keep working and will have "full powers and conditions to keep governing the country."

He said he will be treated at the same medical center in Havana where his cancer was originally detected and where he has undergone three operations.

Last year, Chavez shaved his head during chemotherapy after his hair began falling out as a result of the treatments.

Now, as he starts radiation therapy, some of the potential side effects of the treatments include fatigue, abdominal cramping, nausea or vomiting, said Dr. Michael Pishvaian, an oncologist at Georgetown University's Lombardi Comprehensive Cancer Center who is not involved in Chavez's treatment.

The radiation is usually administered for a short period on a daily basis, Pishvaian said. "I would imagine that he probably could go about his daily activities even being a president."

Following radiation therapy, patients typically need two weeks to a month to recover from the effects of the treatment, Pishvaian said. "Then he should actually be pretty much back to normal, but will be on sort of high alert for watching to see if the cancer comes back again."

As Chavez was finishing his televised remarks, he said: "I'm leaving to continue this battle, the battle for life."

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Associated Press writer Ian James in Caracas contributed to this report.