The announcement comes two months after Chavez was reelected to a third six-year term and indicates that the preeminent socialist leader is preparing for the worst.
“With God's will, like on the previous occasions, we will come out of this victorious," Chavez said in a public address Saturday, the BBC reported.
“There are risks. Who can deny it?” he added, acknowledging the possibility of a less-hopeful outcome.
The severity of Chavez’s illness remains a mystery, as he and his administration refuse to disclose any detailed medical information.
Chavez, 58, declared himself cancer-free in May after receiving multiple radiation therapy treatments in Cuba over the course of a year and undergoing at least two surgeries to remove tumors from his pelvic area.
On Saturday, after returning from a brief medical trip to Cuba, Chavez revealed doctors had discovered “some malignant cells,” according to the Associated Press.
Chavez is due to begin his next term Jan. 10, but if he is unable to return to office within the first four years, new elections must be held, according to the Venezuelan constitution.
In his 14 years as president, Chavez has never identified a clear political successor, adding gravity to the decision to call for his supporters to stand behind Maduro should he be unable to continue leading the country.
Chavez praised Maduro in his address Saturday, saying he would be ready to lead in his place.
“He is a complete revolutionary, a man of great experience despite his youth, with great dedication and capacity for work," Chavez said.
Maduro, 50, is a former bus driver, union leader and later a legislator who has been a longtime supporter and close ally of Chavez.
In addition to his role as vice president, Maduro also serves as foreign minister, a position he has held since 2006.
It remains unclear, however, whether the Socialist Party and its supporters will stand behind Maduro in the event of Chavez’s death or incapacitation.
"Chavez has never prepared his party, let alone his nation, for a successor,” Javier Corrales, professor of politics at Amherst College in Massachusetts, told the Guardian.
"The party leaders are not clear among themselves about [who] deserves to be the successor. ... If he withdraws, no one knows how this inevitable tension will be solved."