Venezuela President Hugo Chavez says he will return to Cuba on Sunday for more cancer surgery, and has spoken openly for the first time of a successor.
In a televised address to the nation, he named his Vice-President Nicolas Maduro as the man to replace him if anything should happen to him.
He only returned from cancer-related treatment in Cuba on Friday.
He said thorough tests undertaken during his stay had detected more cancerous cells.
"Unfortunately, during these exhaustive exams they found some malignant cells in the same area. It is absolutely necessary, absolutely essential, that I have to undergo a new surgical intervention," he said.
"With God's will, like on the previous occasions, we will come out of this victorious."
But, he acknowledged the seriousness of the situation. "There are risks, Who can deny it?" he said.
Mr Chavez said his doctors had recommend he stay in Cuba and undergo surgery this weekend, but he told them he wanted to return to Venezuela first - even though the pain he is experiencing is "not insignificant".
Speaking from the Miraflores presidential palace, Mr Chavez said that if his health failed and a new election had to be held, his supporters should vote for Nicolas Maduro.
Mr Maduro, a former bus driver, is one of the president's closest advisers. He had been foreign minister since 2006 until he was chosen by Mr Chavez to be vice-president following his election win in October.
"He is a complete revolutionary, a man of great experience despite his youth, with great dedication and capacity for work," Mr Chavez said.
Mr Chavez underwent surgery for unspecified type of cancer in the pelvic region after his diagnosis in June 2011, and then had another bout of surgery last February along with chemotherapy and radiation treatments.
He declared himself free of cancer in May.
He was re-elected in October for a fourth term in office, but acknowledged that the campaigning had left him exhausted and in some pain.
He left for Cuba on 27 November saying he would be receiving "hyperbaric oxygenation" therapy, which can ease ailments caused by radiation treatment.
But speculation has been rife that the cancer had returned, prompting the opposition to call for greater transparency about the state of the president's health.
Mr Chavez is due to begin his new six-year term in office on 10 January.
The constitution states that should the president leave office in the first four years of his term then an election must be held within 30 days.