Chavez said Tuesday night that officials certified vast deposits of heavy crude in the Orinoco River basin in December, and that "we have reached 253 billion" barrels of oil.

Last May, the Venezuelan government said its proven reserves stood at 172 billion barrels.

Gustavo Coronel, an energy consultant and former executive of state oil company Petroleos de Venezuela SA, said such a quick increase is technically impossible.

"What the Venezuelan government is doing is imposing an arbitrary, higher recovery factor to the oil that is assumed to be in place," Coronel said. He said that for oil deposits to count as proven reserves they must be recoverable within a reasonable period of time, and that much of the heavy crude in the Orinoco region is not.

Chavez claimed in a televised speech that it is "scientifically proven we're now in the first place in the world in oil reserves." Coronel disputed that.

"There is nothing scientific about this arbitrary upgrading of the recovery factor," Coronel said. "The way the Chavez government is handling this issue is political, not technical, designed to increase the geopolitical clout of his regime."