"The beating we're going to give the Venezuelan right will be memorable ... not just in the history of Venezuela but in almost all the world," he told thousands of red-clad, ecstatic supporters gathered outside the presidential palace.
The 57-year-old socialist leader flew home on Friday after cancer surgery in Cuba, his third operation in less than a year.
His return after a three-week absence thrilled his fans and should quell rumors of his top aides wrestling for power behind the scenes - at least for now.
But so little is known about his health - even what type of cancer he is suffering from has not been revealed - that big doubts remain over whether the normally energetic Chavez will be able to campaign ahead of the October 7 vote.
So Venezuelans have been glued to the images of him since his return. He appeared sure-footed at the airport on Friday, and there were few clues to his condition other than an occasional quiver in his voice during a 30-minute speech after he landed.
Film of him leaving Havana earlier that day showed him quickly climbing the steps to his plane, unaided, after bidding farewell to Cuban leader Raul Castro.
Chavez said on Saturday he will undergo radiation therapy in the coming days, but it is unclear whether that will take place in Caracas or back in Havana.
On Saturday he emerged onto the "Balcony of the People" at the ornate Miraflores palace wearing a tracksuit in the colors of the Venezuelan flag and flanked by officials and relatives.
He sang along with local musicians, danced gingerly with his daughter - to roars of approval from the crowd - and then delivered a forceful speech that lasted almost an hour.
"Chavez, I love you!" shouted some supporters, while others chanted: "The people and God are with you." One held a placard that read: "Onwards comandante, don't forget to rest!"
Some urged the president to put on a hat to guard against the fierce sun. Chuckling, he donned a baseball cap.
'They never play clean'
Soldiers on the roof of a building across the street held their fists aloft and waved a giant Venezuelan flag.
Largely due to his unexpected illness, which was announced last year, the upcoming election has turned into the toughest political battle of Chavez's 13 years in power.
Last June Cuban doctors removed a large cancerous tumor from his pelvis. By the end of the year, Chavez was saying he was completely cured - and supporters were shocked when he returned to Havana last month to have another tumor removed.
Chavez has denied rumors, mostly in opposition-leaning media, that the disease has spread.
But his weakened state contrasts sharply with his opponent: 39-year-old state governor Henrique Capriles, who has embarked on a national "door-to-door" tour in a bid to win over disenchanted "Chavistas."
The latest polls show Chavez in the lead, with one saying on Saturday that 56.5 percent of those surveyed planned to vote for the president, versus 26.6 percent for Capriles.
Whatever his condition, the side effects of the radiation treatment are almost sure to disrupt the president's campaign, whereas normally he would have been expected to crisscross the country meeting voters in person.
From the balcony on Saturday, Chavez continued his steady denunciations of his political rivals.
"They're a minority but they have a lot of economic power, power in the media. And they have no scruples ... . They're dirty. They play dirty. They never play clean, they don't know how."
He scoffed at rumors of infighting and power plays at the top of his ruling Socialist Party as an invention of a desperate opposition that bore more resemblance to a "telenovela," or a TV soap opera, than to reality.
And he called on his supporters to focus on the election.
"We must work hard every day ... . We must not fall into provocations. The central objective is October 7," he said.
"We must strengthen our internal unity with absolute loyalty to the people and the revolution ... . This battle will be hard, but we will win."