ORURO, Bolivia -- President Hugo Chávez of Venezuela announced Saturday in Caracas that he would have to undergo another operation for cancer, and he designated his vice president, Nicolás Maduro, as his successor if he should prove unable to continue to lead the country.
Mr. Chávez, appearing somber and contemplative, made the announcement in a televised address from the presidential palace. Mr. Maduro sat to his left, and several other cabinet members were also present.
It was the first time that Mr. Chávez had said publicly whom he wanted as his successor. Mr. Chávez said that he would fly to Havana on Sunday for the operation. The announcement came just weeks after he was elected to a new six-year term, beginning in early January.
He said Saturday that tests immediately after his re-election found no cancer. But he said he later experienced swelling and pain. He went to Cuba on Nov. 27 for what the government said was hyperbaric treatment meant to aid in healing.
Exhaustive tests at the time found "some malignant cells," Mr. Chávez said.
"With the favor of God, as on the previous occasions, we will be victorious," he added.
But he acknowledged the possibility that he may not be able to continue as president or begin his new term. If he is unable to do so, the Constitution says that new elections would have to be called within 30 days.
In that case, he said, "my strong opinion, as clear as the full moon, irrevocable, absolute, total" is that "you should elect Nicolás Maduro" as the new president.
"I ask it from my heart," he added.
Mr. Chávez said that he was in a significant amount of pain and that his doctors had urged him to have the operation no later than Friday, but he had insisted on postponing it so that he could return briefly from Cuba, where he had been undergoing medical treatment. He flew back to Caracas on Friday.
Mr. Chávez first received a cancer diagnosis in June 2011. He had surgery and chemotherapy, but in February he said the cancer had returned. He then had another operation, followed by radiation treatment.
He has refused to say what kind of cancer he has, or exactly where in his body it had appeared.
Mr. Maduro is a former bus driver and legislator who has served for years as Venezuela's foreign minister.
This article originally appeared in The New York Times.