Several Latin American leaders were expected to travel to Venezuela in a show of support for President Hugo Chavez, whose inauguration has been postponed due to his poor health.
The 58-year-old left-wing nationalist leader who was re-elected in October is being treated for cancer in Cuba. He suffered respiratory failure last week after a fourth round of surgery.
His deputy and appointed successor Nicolas Maduro on Tuesday informed parliament that Chavez would not be sworn for a fourth term Thursday but would take the oath in the Supreme Court later.
Bolivian President Evo Morales, Uruguayan President Jose Mujica and their Haitian counterpart Michel Martelly said they would still travel to Caracas.
Colombian media reported President Juan Manuel Santos had cancelled his trip but would send a representative.
Venezuela's opposition has accused the government of violating the constitution and called for parliament president Diosdado Cabello to take over in Chavez's absence.
The government argues that Chavez had permission from parliament to take care of his health and that the swearing-in ceremony was not compulsory.
It has called a rally of Chavez supporters outside the presidential palace.
"Take, commander, all the time that you need to get well... There is no power vacuum here," Cabello said in parliament.
The Venezuelan Bishops' Conference has urged the authorities to give "clear and truthful" information on Chavez' health, saying A team of Venezuelan medical experts should "dissipate uncertainty".