But some of Chavez's close confidants dismiss the view that the inauguration date is a hard deadline, saying Chavez could be given more time to recover from his surgery if necessary.
Cabello noted last month that the constitution says if a president is unable to be sworn in by the legislature, he may be sworn in by Supreme Court justices, who were appointed by the mostly pro-Chavez legislature.
"When? It doesn't say. Where? It doesn't say where," Cabello recently told a crowd of government supporters. His indication that the constitution does not specify where a president-elect should be sworn in by the Supreme Court has led to speculation that justices could travel to Cuba for the ceremony.
Opposition leaders chafe at the suggestion that Chavez could take office from a foreign country, saying the president made it clear before he left for the operation that his health was deteriorating by designating Maduro as his successor.
Aristobulo Isturiz, a state governor and leader of Chavez's United Socialist Party of Venezuela, said Thursday that if Chavez's swearing-in isn't held Jan. 10, it will be up to the Supreme Court to determine the place and date of the ceremony.
"The president has a right to recover," Isturiz said in remarks published by the state-run Venezuelan News Agency.
More than three weeks after Chavez's cancer surgery, government officials have been providing vague and shifting updates on his condition. Maduro announced over the weekend that Chavez had suffered complications due to a respiratory infection and was in "delicate" condition.
The vice president initially had said he would return from Cuba to Venezuela on Wednesday, but stayed another day while visiting Chavez along with Cabello and others.
Maduro said Chavez's respiratory problems "have seriously affected him."
Still, Maduro expressed hope: "In our hearts, we feel it, sooner rather than later we're going to see commander Hugo Chavez here in his homeland, here with us."
Caracas Mayor Antonio Ledezma, an opposition politician, proposed earlier Thursday that a commission travel to Cuba to determine the state of Chavez's health. He said the delegation should be made up of doctors, lawmakers and other officials such as state governors, including opposition leader Henrique Capriles.
"I'm not asking for permission to go to Cuba. I think it's our right to go there and see what's going on," Ledezma said in comments reported by the television channel Globovision. "Enough mysteries. Venezuela isn't a colony of Cuba."
Some of the brewing disagreements could begin to be aired Saturday, when the National Assembly, which is controlled by a pro-Chavez majority, convenes to select legislative leaders. That session will be held just five days before the scheduled inauguration day.
Law professor Vicente Gonzalez de la Vega agrees with Cabello's view that the constitution is ambiguous regarding the time and place of a swearing-in ceremony before the Supreme Court.
Supreme Court President Luisa Estella Morales said following Cabello's proposal last month that justices could rule on whether it's constitutional to postpone the date of the swearing-in ceremony. The issue has not yet been brought before the court, but Morales said Dec. 20 that the court could take up such issues if asked and would have the final word.
Before Chavez's inauguration date could be postponed, Gonzalez said, lawmakers would have to approve a 90-day extension of Chavez's "temporary absence" granted for his trip to Cuba for surgery. The president of the National Assembly would then be sworn in as an interim president for 90 days, said Gonzalez, a professor at the Central University of Venezuela.
In order for that to occur, though, Gonzalez said the Supreme Court would need to appoint a panel of doctors to examine Chavez to determine whether his health could improve and whether he might be capable of continuing his duties as president.