CARACAS: President Hugo Chavez is making progress as he recovers from cancer surgery in Cuba, his vice president said Tuesday after returning from a trip to Havana to visit the Venezuelan leader.

Chavez, who has been battling complications since undergoing surgery more than a month ago, is "climbing the hill, he is advancing," said Vice President Nicolas Maduro.

Maduro, who returned overnight after a three-day visit to Havana, said he and other members of the government had spoken with Chavez over the past few days about national matters in the country with the world's largest proven oil reserves.

"We saw him up until yesterday," he said, adding that they had updated the ailing leader on "how our people is progressing."

Maduro spoke at a meeting with the nation's governors.

The government's most recent status report on Chavez's health said he has shown improvement in recent days but is still suffering from a "respiratory insufficiency" caused by a severe pulmonary infection.

In office since 1999, Chavez was too sick to make it to his own inauguration on January 10, so his swearing-in has been indefinitely postponed. Congress approved the delay and the Supreme Court upheld it, much to the chagrin of opposition parties. Chavez was re-elected October 7 to a third six year term.

Since being diagnosed with cancer in mid-2011 he has undergone surgery four times.

Among those who returned from Havana with Maduro were National Assembly speaker Diosdado Cabello, Oil Minister Rafael Ramirez, Solicitor General Cilia Flores and Adan Chavez, the president's brother.

Filling in for Chavez, Maduro was to address the National Assembly later Tuesday in a speech summing up the state of the country as of the end of 2012. Before leaving for Havana a month ago, Chavez appointed Maduro to be his political heir.

The address is mandated by the constitution and Tuesday was the last day it could be delivered. The address has to be delivered in person.

When Chavez delivered the address a year ago, he spoke for nine hours.

A month later he was diagnosed with a relapse and underwent his fourth cancer operation. The government has never said the type of cancer he is suffering from or exactly where it is located.

Meanwhile, the United States and Colombia said Tuesday that any political transition undertaken in Venezuela must respect its constitution.

This appeal was made by Secretary of State Hillary Clinton and her Colombian counterpart, Maria Angela Holguin, who met in Washington and discussed the situation in Venezuela, State Department spokeswoman Victoria Nuland said.

Venezuelan opposition leaders are angry that the Chavez government remains in power even though he missed his scheduled inauguration last week. They say that, as per the constitution, the speaker of the National Assembly should temporarily assume the presidency.

Clinton and Holguin discussed prospects for change in Venezuela and said any transition should be transparent and democratic, Nuland said.

The Unites States has had tense relations with Venezuela under Chavez, who has irked Washington by depicting the United States as imperialist and aligned his country with countries such as Iran, Syria and Cuba.