CARACAS, Venezuela (AP) — Venezuelan President Hugo Chavez is being treated for "respiratory deficiency" after complications from a severe lung infection, his government said, pointing to a deepening crisis for the ailing 58-year-old president.

Chavez hasn't spoken publicly or been seen since his December 11 operation in Cuba, and the latest report from his government Thursday night increased speculation that he is unlikely to be able to be sworn in for another term as scheduled in less than a week. It was the first time the government has described the lung infection as "severe," and the strongest confirmation yet that Chavez is having serious trouble breathing after days of rumors about his condition worsening.

"Chavez has faced complications as a result of a severe respiratory infection. This infection has led to respiratory deficiency that requires Commander Chavez to remain in strict compliance with his medical treatment," Information Minister Ernesto Villegas said Thursday night, reading the statement on television.

The government's characterisation raised the possibility that Chavez might be breathing with the assistance of a machine. But the government did not address that question and didn't give details of the president's treatment.

Independent medical experts consulted by The Associated Press said the government's account indicated a potentially dangerous turn in Chavez's condition, but that it's unclear whether he is attached to a ventilator.

"It appears he has a very severe pneumonia that he suffered after a respiratory failure. It is not very specific," said Dr. Alejandro Rios-Ramirez, a pulmonary specialist in Puerto Vallarta, Mexico, who is not involved in Chavez's treatment. "It does imply the gravity of his pulmonary infection that led to a respiratory failure."

Dr Gustavo Medrano, a lung specialist at the Centro Medico hospital in Caracas, said he has seen similar cases in cancer patients who have undergone surgery, and "in general it's very bad, above all after a surgery like the one they performed on him."

"I don't know the magnitude of the infection he has, how much of his lungs have been compromised, how much other organs are being affected. That's not clear," Medrano said.

"What's most likely is that he's on mechanical ventilation," Medrano added. However, he said, while respiratory deficiency means there is an abnormally low concentration of oxygen in the blood, depending on the severity it can be treated in various ways.

Dr Michael Pishvaian, an oncologist at Georgetown University 's Lombardi Cancer Centre in Washington, agreed that such respiratory infections can run the gamut from "a mild infection requiring antibiotics and supplemental oxygen to life-threatening respiratory complications."

"It could be a very ominous sign," Pishvaian said. He said it's possible Chavez could be on "life support," but added that it's impossible to be sure without more details.

The government expressed confidence in Chavez's medical team and condemned what it called a "campaign of psychological warfare" in the international media regarding the president's condition. Officials have urged Venezuelans not to heed rumours about Chavez's condition.

The statement didn't point to any particular rumours but said "this campaign aims ultimately to destabilise the Bolivarian Republic of Venezuela ... and end the Bolivarian Revolution led by Chavez."