Chavez has been recovering favorably despite some "moments of tension" after Tuesday's surgery and is now in a "process of stabilization," Science and Technology Minister Jorge Arreaza said on Venezuelan television in a phone call from Havana.
It's unclear when Chavez might be well enough to return home, but Information Minister Ernesto Villegas expressed hope it could be soon. Chavez, who was re-elected in October, is due to be sworn in for another six-year term on Jan. 10.
"We're extremely hopeful that the president may be with us very soon. But it would also be irresponsible on my part to speak of dates," Villegas told The Associated Press.
"We're confident that President Chavez will be here to take office on Jan. 10. Now, in the event that weren't possible, our people would have to be prepared to understand it," Villegas said.
He spoke during a ceremony in downtown Caracas attended by Vice President Nicolas Maduro and other government officials as well as visiting leaders from other countries.
Arreaza's phone call became the centerpiece of the televised ceremony, and he said Castro has come to see Chavez every day since the surgery.
"He always stops by to personally find out about El Comandante's health condition and also to share his knowledge with all of us, and to give the family courage and encouragement," said Arreaza, who is the husband of Chavez's eldest daughter, Rosa.
Chavez has long shared a close friendship with the former Cuban president, describing him as being like a father and mentor.
The 58-year-old Venezuelan leader underwent his fourth cancer-related operation in Cuba after tests found the illness had come back despite previous operations, chemotherapy and radiation treatments. He previously had said in July that tests showed he was cancer-free.
Throughout his treatments in Cuba, Chavez has kept secret some details about his pelvic cancer, including the exact location and type of tumors removed.
Venezuela's government has said Chavez suffered complications during a complicated six-hour surgery but has since been recovering progressively.
Arreaza said there had been "moments of tension, above all on (December) 11 and 12, but we've overcome them one by one."
"The president has begun to communicate with his close relatives," he said. Arreaza said that as Chavez began to speak, he told him of "his deep love for his people."
"El Comandante has fought a great battle, and, as he told us, he will overcome each of these moments little by little. He's getting better," Arreaza said.
Chavez also called for his supporters to vote in Venezuela's gubernatorial elections Sunday, Arreaza said.
"He is now completely in full intellectual conditions to send this message to the Venezuela," Arreaza added.
Maduro told Arreaza to give Chavez a message: "Tell him that the people here are on their feet working, battling." Maduro expressed confidence that Chavez's allies will win Sunday's elections.
Maduro also said National Assembly President Diosdado Cabello made a quick trip to Havana on Friday along with Attorney General Cilia Flores and they were in contact with Chavez's family.
"Praying together, we're going to achieve the miracle," Maduro said.
The vice president, whom Chavez recently designated his preferred successor, also repeated his government's condemnation of President Barack Obama's criticisms this week of "authoritarian policies" in Venezuela. Maduro called Obama's comments "unacceptable."
Saturday night's ceremony was held on the eighth anniversary of the creation of the leftist Bolivarian Alliance, or ALBA, bloc of nations, which includes Venezuela, Bolivia, Cuba and other nations.
Maduro read aloud a letter from Castro in which he said "the name of Hugo Chavez is admired and respected throughout the world." The former Cuban president was quoted as writing that "the doctors are fighting with optimism" for Chavez's recovery.
Bolivian President Evo Morales, who attended the event in Caracas, told the television network Telesur that he hadn't yet been able to travel to Cuba but that he hoped to meet with Chavez soon. He didn't give details.
Chavez's daughter Maria, who was with the president in Havana, thanked supporters for their prayers in a message on her Twitter account.
"We are continuing to battle along with papa," she said, expressing trust in "the hand of God!"
Associated Press writers Vivian Sequera and Ian James contributed to this report.