Public New Year's celebrations were cancelled after a rare acknowledgement of the weakening state of health of President Chavez, 58.

Nicolas Maduro, the vice-president and his heir apparent warned of a new setback following cancer surgery in Cuba and admitted that the leader faced an uphill battle.

"We were informed of new complications arising from the already known respiratory infection," Mr Maduro said late on Sunday in a sombre televised address from Havana, where he was at President Chavez's bedside.

"President Chavez's state of health continues to be delicate," Mr Maduro added, warning that the complications "are being attended to in a process that is not without its risks."