Venezuelan government officials say Chavez has developed a "respiratory deficiency" after developing a lung infection in Cuba, where he is hospitalized following cancer surgery, Sky News reported Saturday.
The status of Chavez's health and his invisibility during his three-week stay in Cuba have created a power vacuum, the report said.
Chavez opponents say Venezuela must hold new elections within 30 days if he isn't well enough to attend his swearing. Supporters say he should be given time to recover, even though no one knows if he is getting better.
Vice President Nicolas Maduro claims Chavez can continue in office even if he is unable to take the oath.
The Venezuelan Constitution requires a new election if the president dies or suffers permanent physical or mental disability before being sworn in, The Guardian reported.
It says the president-elect can take the oath of office in the presence of Supreme Court justices -- who are mostly Chavez appointees -- but was unclear whether he can he do that in a hospital abroad, the report said.