Denis Goldberg, a friend of Mandela for more than five decades, told the weekly 'City Press' that the matter of switching off the life support had been discussed and dismissed.
"I was told that the doctors said they would only consider such a situation if there was a genuine state of organ failure," Goldberg said, as the 94-year-old leader spent nearly one month in the hospital.
Confirming that Mandela was breathing with assistance from machines, Goldberg told the weekly: "But he responds to voices and tries to talk, yet mumbles."
"He was dozing when I got there. I spoke and told him who I was and he opened his eyes and looked at me. I spoke to him for about 10 minutes and he responded positively to what I was saying.
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"He did not answer because he can't talk, with the pipe in his throat, but he was moving his jaw as if he wanted to talk."
Court paper filed earlier this week in a bitter feud between Mandela family members cited Mandela's health as being in a "permanent vegetative state", but this was rejected by the Presidency which said Mandela remained in a critical but stable condition.
The court document had said that Mandela's doctors advised his family to turn off the ailing icon's life-support machines.