(CNN) — (CNN) -- Health problems have stopped Venezuelan President Hugo Chavez from coming to Caracas for an inauguration ceremony Thursday, but there still could be plenty of pomp and circumstance.
Several Latin American leaders have already arrived in Venezuela's capital for an event to honor the ailing Chavez, who is undergoing cancer treatment in Cuba and has not made a public appearance in a month.
As speculation surges about his health and the country's political future, Chavez's party has called for supporters to gather in front of the presidential palace Thursday to show solidarity.
The rally comes as authorities continue to reassure Venezuelans that Chavez's government remains unified and intact, just days after announcing that Chavez, 58, wasn't well enough to be sworn in on Thursday -- specified by the constitution as inauguration day.
Uruguayan President Jose Mujica, Bolivian President Evo Morales and Nicaraguan President Daniel Ortega will attend, officials have said.
Opposition politicians have argued that delaying Chavez's swearing-in for a new presidential term leaves no one in charge of Venezuela once the current term ends. Chavez allies -- including a majority of lawmakers in the country's congress -- have said he should remain in power while taking the time he needs to recuperate.
On Wednesday, Venezuela's Supreme Court backed the government's position, ruling that Chavez begins a new term on Thursday and can be sworn in later before the court.
But several key questions remain unanswered: How long will Chavez be in Cuba for cancer treatment? How dire is his medical situation? And will simmering political tension about who's running the country boil over?
Last week, a government spokesman said Chavez was battling a severe lung infection that has caused respiratory failure.
Earlier this week, his condition remained unchanged, the government said in a statement Monday.
"Treatment has been administered permanently and rigorously, and the patient is supporting it," the statement said.
While reports from CNN affiliate Globovision Wednesday included discussions of political uncertainty, state television broadcasts showed presidents and foreign ministers arriving in Venezuela, walking on a red carpet at the airport as soldiers stood guard.
Officials have planned a "beautiful event" in honor of Chavez, Venezuelan Vice President Nicolas Maduro said Wednesday.
Meanwhile, Venezuelan opposition leaders called on officials from other countries to cancel their plans to attend.
Henrique Capriles, who lost to Chavez in October's presidential vote, said he had reached out to foreign ministries to ask them not to send representatives.
"They are trying to put presidents from the Americas in a political rally," he said.