Venezuelan President Hugo Chavez will not take the oath for a new term in office on Thursday, the government has said.
Mr Chavez is in hospital in Cuba after cancer surgery, and has suffered complications caused by a lung infection.
He has not been seen in public since his operation last month.
Venezuela's opposition has called for the Supreme Court to rule on what should be done if Mr Chavez is absent.
Its leader, Henrique Capriles, says that if Mr Chavez is not sworn in, then according to the constitution the National Assembly speaker should act as caretaker president until new elections are held within 30 days.
The government insists that the inauguration is a mere formality for an incumbent leader.
Mr Chavez has been president since 1999.
Show of support
Announcing the news to legislators, National Assembly speaker Diosdado Cabello said Mr Chavez would be sworn in at a later date before the Supreme Court, according to Article 231 of the Constitution.
"On the recommendation of his medical team, the process of post-operation recuperation will have to be prolonged beyond 10 January, [as a result of which] he will be unable to present himself on this date to the National Assembly." he said, reading a letter from Vice President Nicolas Maduro.
Earlier, Mr Cabello called on Chavez supporters to take to the streets of Caracas on Thursday to show support for him.
He said several foreign leaders had agreed to be at the Miraflores Presidential Palace on inauguration day.
But Mr Capriles urged them to stay away and not succumb to "a game by a political party", meaning Mr Chavez's ruling party.
In his most recent update on Mr Chavez, Information Minister Ernesto Villegas said his condition was "stable", and he was "responding to the treatment".