After almost 14 years in power, Venezuelan President Hugo Chavez seeks a new six-year term on Sunday, but he faces his toughest challenge yet from youthful opposition rival Henrique Capriles.

The leftist leader retains a loyal following among the country's poor, who have propelled him to easy victories in past elections, but Capriles has surged in opinion polls after an energetic door-to-door campaign across the country.

While he remains the odds-on favorite, Chavez has urged his supporters not to declare victory too early and to turn out to vote en masse on Sunday. He also charges that the "far right" plans not to recognize his victory.

The 58-year-old leader, who was operated twice for cancer and underwent chemotherapy in the past two years, stepped up his campaign this week with giant rallies that climaxed with a massive demonstration in Caracas on Thursday.