Updated

Venezuelan President Hugo Chavez said he is certain he will pursue his re-election bid next year even as he struggles to overcome cancer.

Chavez said in an interview published Monday in the government newspaper Correo del Orinoco that he hasn't "for an instant thought about withdrawing from the presidency."

He said if there were physical reasons to step down he would do so but that he is pursuing his candidacy "with more strength than before."

"I'm resolved to reach 2031," Chavez said.

The leftist president has been in office since 1999 and is seeking another six-year term. He has suggested in the past that he hopes to keep winning re-election to remain president for many years to come. He has vaguely mentioned various dates, ranging from 2021 to 2031.

A poll released last week said Chavez's public approval rating remains at 50 percent and hasn't significantly varied since his cancer diagnosis.

Chavez completed his first phase of chemotherapy in Cuba last week. He said he is now waiting for additional phases of chemotherapy but did not say how soon the treatments would resume or how long the process could last.

Chavez underwent surgery in Cuba on June 20 to remove a cancerous tumor, which he has said was the size of a baseball. He hasn't said what type of cancer he has been diagnosed with or specified where exactly it was located, saying only that it was in his pelvic region.

Chavez, who turns 57 on Thursday, said he plans to celebrate his birthday in Venezuela.

He dismissed what he called the "macabre, perverse, morbid wishes of some commentators like Roger Noriega," a former U.S. assistant secretary of state under former President George W. Bush.

A message on Noriega's Twitter account on Sunday said he believes Chavez's "health is grave" and that the opposition "should fill vacuum/prepare for any scenario."

Chavez said after his return from Cuba to Venezuela on Saturday night that thorough tests found no signs that any cancer cells have reappeared.

Chavez gave a speech and sang at a public event on Sunday, appearing upbeat and energetic.