By Anthony Boadle and Daniel Wallis
CARACAS (Reuters) - Feisty Venezuelan President Hugo Chavez acknowledged on Friday that radiation treatment for cancer was wearing him down, but he vowed to squash his opponents in October's presidential election.
Ramping up the political rhetoric at a huge rally to mark the 10th anniversary of his return to power after a brief coup, Chavez said three sessions of radiation therapy in Cuba had taken their toll.
But he was more combative than usual, vowing to win the October 7 "by a knock-out," repeatedly denouncing his opponents as upper-class "bourgeoisie losers," and launching a new anti-coup force that would prevent any repeat of the events of 2002.
"I continue to recover from the surgery. The radiation has an impact on my body, it has some impact on my physical strength, but I am doing well. We will be alright, thank God," he told tens of thousands of supporters clad in red T-shirts in honor of his ruling Socialist Party.
Chavez, 57, said his doctors had not decided whether he was fit to attend a summit of the hemisphere's leaders, including U.S. President Barack Obama, this weekend in Colombia.
If he did attend, it would only be for a few hours before continuing on to Havana for a fourth session of radiation treatment. This time, he told the rally from the balcony of the Miraflores presidential palace in Caracas, he would spend the whole week in Cuba - longer than his recent trips.
The president said he wanted to avoid "coming and going."
His frequent visits to a tightly guarded hospital on the Communist-led island means he is taking himself off the political stage for much of the time, just as the opposition's candidate Henrique Capriles pushes on with a national campaign.
The political temperature has heated up with the coup anniversary. All week, state TV has played video of the dramatic events of April 11-13, when big marches by both sides clashed in the streets around Miraflores and about 20 people died.
Chavez was ousted from power for two days until giant demonstrations by his supporters, and allies in the military, returned him to power in a saga that has taken on almost religious overtones for some passionate "Chavistas."
A decade later, they still fume at the illegality of how he was ousted from office. It is also an emotional date for some in the opposition who had a brief taste of long-sought power and a sense of what a post-Chavez Venezuela might feel like.
Others in the opposition were happy to see him replaced, if only temporarily, but remain upset by how it happened.
Chavez routinely accuses his political foes of plotting another attempt to seize power by force.
"Prepare yourselves to receive the biggest and most crushing defeat," he said as the crowd cheered.
He gave very few details of the new anti-coup force he launched on Friday, but his fiery comments set the stage for a bitterly contested election.
They follow threats he made recently to nationalize private banks and any other local businesses that he said were supporting the opposition in its "violent plan" to topple him.
"We will make them repent forever," he said last month.
While he has a solid 13 percentage point lead over Capriles in the most recent poll published last month [ID:nL2E8ERPC2], many Venezuelans remain undecided and Chavez faces his toughest electoral challenge.
His illness has cast further doubt over the future of the man who has dominated politics in South America's biggest oil exporter during his 13 years in office.
Very little is known about Chavez's health, including the type of cancer he is battling. He has undergone three operations in Cuba in less than a year and rumors persist that he is more ill than he has admitted.
(Editing by Stacey Joyce)