Venezuela's vice president has said that president Hugo Chavez faces a "complex and hard" process after undergoing his fourth cancer-related operation in Cuba.
Nicolas Maduro made the announcement a day after Mr Chavez's surgery, appearing on television with a sad expression, alongside other top allies of the president.
"It was a complex, difficult, delicate operation," Mr Maduro said, indicating "the post-operative process is also going to be a complex and hard process".
The vice president, whom Mr Chavez named over the weekend as his chosen political heir, was flanked by National Assembly president Diosdado Cabello and oil minister Rafael Ramirez, who had accompanied the president in Havana during the surgery.
Mr Maduro said Mr Cabello and Mr Ramirez had returned to Caracas in the early hours and that they had talked about the situation until daybreak. Mr Maduro's voice was hoarse and cracked at times.
Without giving details, Mr Maduro reiterated Mr Chavez's recent remarks that the surgery presented risks and that people should be prepared for any "difficult scenarios, which can be faced only with the unity of the people".
"We're more united than ever," Mr Maduro said while Mr Cabello and Mr Ramirez stood solemnly. "We're united in loyalty to Chavez."
The vice president criticised the opposition, accusing it of using Mr Chavez's illness to attack him. Some political adversaries have said the president should be more forthcoming about details of his pelvic cancer.
The morning after the operation, Venezuelan state television showed a Mass where the president's supporters prayed for him.
The 58-year-old president won re-election in October and is due to be sworn in for a new six-year term on January 10. If Mr Chavez were to die, the constitution says that new elections should be called and held within 30 days.