Venezuelan President Hugo Chavez can work on government issues and is "very energetic" despite being hospitalised and breathing through a tube, a top aide said Saturday.

The 58-year-old president has not been seen or heard from since Monday, when he returned to Caracas from cancer surgery in Cuba, to lead this OPEC member state sitting atop the world's largest crude oil reserves.

"The president continues to breathe through a tracheal tube, but he is able to communicate with us through written notes and give us instructions," Vice President Nicolas Maduro told local television.

During more than five hours spent with Chavez in his hospital room on Friday, Maduro said they were able to discuss several issues, specifically military affairs and the economy.

"He was very energetic, had a lot of spirit and vitality, and that's what we wanted to tell the people despite the late hour," Maduro said.

"We have reviewed a number of subjects, and he told us about being extremely happy to be in Caracas, the city of his heart."

Since his last surgery, the only photos released of Chavez came out almost a week ago. He was seen bedridden but smiling, looking through a newspaper with two of his daughters at his side.

In Brasilia, President Dilma Rousseff said she got a report on Chavez's condition from Venezuelan Foreign Minister Elias Jaua, and that it did not seem to her "very worrisome" on Saturday.

Jaua said "everything was under control," Rousseff added. "He did not give me a very worrisome condition."

But Chavez has "worsened in terms of his breathing, and even had trouble breathing," Rousseff said, the leftist leader was said to be doing "quite well."

At the Caracas military hospital where Chavez is said to be continuing his convalescence, soldiers are on guard outside to keep out journalists and curious onlookers.

Chavez had declared himself free of cancer after earlier rounds of surgery and went on to win another six-year term in October elections.

But he later suffered a relapse and after the latest surgery in Havana on December 11, he was too sick to return to Venezuela for his scheduled inauguration on January 10.

The inauguration has been postponed indefinitely, prompting the opposition to cry foul. Vice President Nicolas Maduro, Chavez's handpicked heir, has essentially been running the country in Chavez's absence.

And opposition forces are scrambling to organize ahead of possible early elections, in case Chavez does not get well.

Antonio Ledezma, a leader of the political party Alianza Bravo Pueblo, said various opposition forces would start working Sunday on a unity candidate to run against Maduro.

"The people will be sure to have a unity candidate... who won't be someone who makes his political speeches negative, insulting people like Maduro does," Ledezma said.