(CNN) -- Venezuelan President Hugo Chavez wasn't well enough to give his annual state of the union speech on Tuesday and hasn't been seen publicly in more than a month. But that didn't stop the country's vice president from announcing a high-level appointment in Chavez's name.
Elias Jaua will now be Venezuela's foreign minister, Vice President Nicolas Maduro told lawmakers on Tuesday, saying Chavez had just designated Jaua as the man for the job.
The surprise appointment Tuesday was the latest twist in a political drama that has intensified in the South American country ever since Chavez headed to Cuba for cancer surgery last month. For weeks, supporters and opponents of Chavez have been sparring over an increasingly contentious question: Who's running the country?
Tuesday's Cabinet post announcement quickly became a topic of fierce debate. Some opposition politicians questioned whether Chavez had actually nominated a new foreign minister, or whether Maduro had effectively taken over the presidency. Government officials maintained that Chavez was in charge.
Jaua, long a close ally of Chavez, had been Venezuela's vice president until he stepped down to run for a state governor post last year.
"Now the fundamental task is defending political stability, the unity of Venezuela and national independence," Jaua told reporters. "And we are going to defend it just as much on internal and international fronts."
Maduro had been expected to deliver Tuesday's state of the union address in Chavez's place before Venezuela's National Assembly.
But instead, he handed the assembly's president a written document outlining the government's accomplishments over the past year and gave a speech that lasted less than 10 minutes.
It was a sharp contrast to last year's state of the union, when Chavez spoke for more than nine hours.
Chavez, Maduro said, remains in Cuba undergoing medical treatment.
"Everyone knows why he isn't here personally," Maduro said. "He is pressing on uphill. He's fighting on with his spirit, his vision, his love as a man full of will, life and dedication to the fatherland."
Before he left for Cuba, Chavez said he wanted Maduro to assume the presidency if he becomes incapacitated and called on voters to support him at the polls.
A group of opposition lawmakers walked out in the middle of Maduro's speech in protest on Tuesday.
"I decided to walk out of the National Assembly 'session' because Maduro is violating the constitution by trying to supplant the functions of the president," Maria Corina Machado, an opposition lawmaker, said in a Twitter post.
Machado said Maduro's appearance before lawmakers Tuesday and his announcement of the Cabinet appointment send a clear message: "They are recognizing that there is no president."
Another leading opposition politician said on Tuesday that he wanted to see who signed the decree naming Jaua as foreign minister.
If Maduro signed such a document, that would mean he's taken over the presidency, said Henrique Capriles Radonski, who defeated Jaua in the governor's race in Venezuela's Miranda state last month and lost to Chavez in last year's presidential election.
But government officials have maintained that they are closely following the constitution, and Chavez is still in charge of the country.
"We are united from the bottom of our hearts and are united in loyalty to a man who has the supreme command over this republic and over us," Maduro said on Tuesday. "That man is Hugo Chavez."
On Sunday officials said Chavez's health was progressing positively and that the 58-year-old Venezuelan president was conscious and in contact with his family and political and medical advisers.
"In spite of the delicate state of his health ... the general medical evolution has been favorable in recent days," a government statement said, noting that a lung infection Chavez has been battling was under control.
Neither Chavez nor the government has said what type of cancer he has, sparking growing speculation about his health and political future. Opposition politicians have decried the lack of transparency, while government officials have accused political opponents and right-wing media of trying to destabilize the government by spreading rumors.
Chavez has not made a public appearance or spoken on state television since doctors operated on him more than a month ago. The long absence is not typical of the loquacious leader, who missed his own inauguration last week.
Venezuela's government still held a symbolic swearing in ceremony, with Maduro leading throngs of supporters outside the presidential palace in an oath of "absolute loyalty to the leadership of Comandante Hugo Chavez."
CNN's Rafael Romo and Dana Ford and journalist Osmary Hernandez contributed to this report.