Chavez arrived in Cuba on Saturday, saying he would stay for a week and return healthier. [EPA]

Venezuelan President Hugo Chavez is back in Cuba to begin a second round of chemotherapy treatment following the removal of a cancerous tumour in June.

Chavez, 57, said before leaving on Saturday that he would return to Venezuela within a week "in better condition that I am now".

"We will come out of this stronger. I am sure of it. My perspective is lengthening, and it's not 2012, but 2031," he said before his departure from Caracas, referring to his plans to run for a third six-year term in presidential elections next year.

He said his treatment could begin on Monday, depending on the results of medical tests.

Chavez said last month he had "successfully" finished a first round of chemotherapy after an operation in Cuba in June for a cancerous tumour in his pelvic area.

He said no malignant cells had been found in his body.

"There will be several rounds in order to win this battle and eliminate all risk of malignant cells," he said.

The Venezuelan government has not disclosed the extent of Chavez's cancer or provided any other details, but when Chavez appeared on state television last week, it appeared that he had lost almost all of his hair.

Chavez was accompanied by his daughter Maria Gebriela and met at the airport in Havana by Cuban President Raul Castro. The National Assembly had on Saturday voted unanimously to authorise Chavez to leave the country.

Cuba is Chavez's closest regional ally. Before leaving Caracas, Chavez warned of plans by the United States to destabilise Venezuela and implied that US interference had caused recent social uprisings in the Arab world.

"I was in Tripoli last November with Gaddafi, we strolled along some streets. In Damascus with President Bashar, his wife was driving the car, and we visited some villages. A peaceful country and look at what's going on now. Sadly, that is the empire's plotting," he said.