Maduro, speaking while touring a pediatric hospital, said Chavez is "consolidating a recovery process, which fills us with joy." A day earlier, Maduro said he had received an update from a ruling party member who visited Chavez in Cuba and that the Venezuelan leader's "condition is becoming increasingly stable."
"Prayers are always in our mind in this battle for life that is consolidating itself day by day," Maduro said.
Chavez underwent surgery Dec. 11, about two months after being elected to another six-year presidential term. It was his fourth cancer-related operation since June 2011.
Bolivian President Evo Morales traveled to Cuba on Sunday morning but there was no word on whether he visited his close ally Chavez.
Cuba's government-run newspaper Juventud Rebelde said Morales visited Havana "to express his support for Venezuelan President Hugo Chavez Frias." The Bolivian leader was greeted by Cuban President Raul Castro and the newspaper published a photograph on its website showing the two leaders smiling.
Despite his optimistic tone, Maduro offered no hint about when Chavez might return to Venezuela. Government leaders have warned Venezuelans that Chavez might not be back in time for his Jan. 10 inauguration, raising the possibility of a legal dispute on who should then take over the presidency.
National Assembly President Diosdado Cabello said Saturday that ruling party lawmakers, who hold a majority in the legislature, won't call a new presidential election if Chavez can't return from Cuba in time for the swearing-in ceremony.
But opposition leaders argue that the constitution does not allow for a president's inauguration to be postponed. They have criticized the lack of information on Chavez's long term prognosis and the confusion surrounding the inauguration as an example of the government's disdain for democratic rule of law.
Maduro, Chavez's designated successor, has stepped up his public appearances since the president left, in a clear effort to project continuity and unity within the leftist "chavista" movement. On Sunday night, state television showed Maduro holding a Cabinet meeting on government plans for next year.
Government leaders have worked to keep Chavez present in spirit, even playing recordings of the flamboyant leader singing the national anthem at the start of each event. At the same time, there have been suggestions that Venezuelans should contemplate a future without Chavez, who has dominated life in the South American country for 14 years.
On Sunday, Defense Minister Diego Molero said the Venezuelan armed forces would be loyal to Chavez's movement with or without the president, though he was careful to add that he expected Chavez to return to Venezuela.
"In the event of the absence of our commander in chief—a scenario we are certain will not occur—the National Bolivarian Armed Forces knows what to do, is completely prepared, in the sense of continuing, ideologically, the path of the last 14 years," Molero said.
Associated Press writer Anne-Marie Garcia in Havana contributed to this report.