Venezuela VP: Chavez can delay oath and stay in power
Vice-President Nicolas Maduro said the Supreme Court could swear in Mr Chavez at a later date.
He dismissed opposition calls for new elections should Mr Chavez not attend.
President Chavez is in Cuba struggling to recover from his latest round of surgery to treat cancer.
He has not been seen in public since the operation more than three weeks ago.'Don't mess'
Observers have different interpretations of what it would mean if Mr Chavez misses his inauguration on Thursday.
Some in the opposition have said that if Mr Chavez is still in Cuba, power should pass to the head of the national assembly, and new elections should be held within 30 days.
But Mr Maduro said Thursday was not a fixed deadline, and that there was no reason to declare Mr Chavez's "absolute absence" from office.
"The formality of his swearing-in can be resolved in the Supreme Court," he said.
"The president right now is president," he said, waving a pocket-sized copy of the constitution.
"Don't mess with the people. Respect democracy."
The head of the main opposition coalition, Ramon Guillermo Aveledo, said the government "doesn't want to admit that the president is absent".
"The official version of what is happening is unsustainable," he told reporters.
Officials have said that Mr Chavez, 58, has suffered from complications brought on by a severe lung infection that developed after his latest surgery.
Mr Maduro said the president had "a right to rest and tranquillity, and to recuperate".
"We will have the commander well again."'Unified'
Mr Maduro and National Assembly Head Diosdado Cabello visited Mr Chavez in Cuba earlier in the week, along with several other dignitaries.
The vice-president said President Chavez was "conscious" and had gripped his hand firmly as they discussed Venezuelan politics.
He and Mr Cabello dismissed rumours of a split in the governing socialist movement, after their return from Cuba.
"We're more unified than ever," said Mr Maduro, who Mr Chavez recently named as his preferred successor.
"We swore in front of Commander Chavez that we'll be united at the side of our people," he said.
The National Assembly is due to meet on Saturday to elect its leadership, with Mr Cabello expected to be re-elected.
He has appealed to supporters of Mr Chavez to rally outside parliament during the session.
"If the opposition thinks it will find a space in the National Assembly to conspire against the people, it's mistaken once again," Mr Cabello said on Twitter. "It will be defeated."
Mr Chavez was re-elected to a fourth term as president in October.