Caracas, Venezuela -- President Hugo Chavez has never been one to share decision-making authority. Now, the voluble socialist strongman and acerbic critic of the United States may have no choice but to designate a successor.

His announcement that he will go to Cuba within a week to remove a growth that he says is probably malignant could not come at a worse moment for the leader who is working to transform Venezuela with what he calls "21st century socialism."

With a tight re-election campaign brewing for the president, analysts said Wednesday that Venezuela could be thrown into turmoil because Chavez has resisted grooming a successor during his 13 years in power.

The result is a power vacuum that his camp will be hard-pressed to fill, especially if he is unable to campaign for the Oct. 7 elections or wins and then becomes physically incapable of governing.

"Venezuela is living with the unsettling effects of prolonged, one-man rule," said Michael Shifter, president of the Washington-based Inter-American Dialogue think tank. "Anything can happen."

Shifter said "a fierce power struggle and jockeying for position" is nearly inevitable for Chavez's ruling Socialist Party of Venezuela.

"I promise I will fight without respite for my life," the 57-year-old Chavez tweeted Wednesday.

Chavez did not mention who might replace him during an absence that cancer specialists say could last weeks if the leader has to undergo radiation treatment, as he himself said he expected. Chavez said the same doctors who removed a baseball-size cancerous tumor from his pelvic region in June would be operating on him.

He denied rumors the cancer had spread aggressively, but also said his doctors don't know if the new one-inch lesion they found over the weekend is malignant.

Chavez is expected to travel to Cuba on Friday or Saturday.