He has never revealed the cancer's exact nature or location, prompting opposition politicians and critics to accuse Chavez of a lack of transparency.
Analyst Cynthia Arnson, of the Woodrow Wilson International Center in Washington, said the new surgery seriously complicates Chavez's re-election prospects.
She said: 'It's now clear that Chavez's cancer is far from cured. Chavez's illness - his ability to campaign as well as to govern - is a major factor in the race. It erodes the aura of invincibility as well as inevitability that Chavez has always tried to create.'
The governing party will also be vexed as it lacks an alternative candidate with Chavez's charisma and popular following, Arnson said. She predicted the development will make 'a tight race even tighter' against Capriles.
Chavez insisted he was 'in good physical shape' to confront his new health battle, he said in his phone interview, but later appeared to become emotional as he reflected on mortality.
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