Greek Prime Minister Andreas Papandreou was fighting for survival in the hospital Wednesday, hooked up to life-support systems for his lungs and kidneys.

"The prime minister is not breathing on his own. He breathes entirely because of the machine," hospital spokesman Gregory Skalkeas told reporters.He said Papandreou, 76, was undergoing sporadic dialysis to aid his kidneys in filtering blood, which is expected to continue over the next several days.

"The situation is difficult. All appropriate efforts are being made to face it," Skalkeas said.

Asked by a reporter about reports Papandreou was clinically dead, he replied: "It's not true. His brain is functioning fully and his heart is working without problems."

Papandreou, who was rushed to the hospital with pneumonia nine days ago, was responding to medication, and Skalkeas said doctors would try to take him off the respirator in the next two days.

"He has to get off the respirator very soon to avoid secondary infections which at this point could be fatal," a doctor at the Onassis Heart Center, who requested anonymity, said. "The premier is in critical condition."

Doctors were forced to put Papandreou back on a respirator Tuesday. Athens newspapers said Papandreou was weak and asked his doctors in a whispering voice to leave him in peace.

"Please, let me rest," he was quoted as telling his doctors as they were trying to put him on the respiratory machine.

Papandreou swept to power as Greece's first socialist prime minister in 1981. There is widespread doubt he will be able to serve out his current four-year term, even if he recovers.