Doctors advised turning off Nelson Mandela's life support because he is in a "permanent vegetative state", court documents say.
Medics told Mandela's family they should think about letting him go rather than "prolong his suffering", reported The Telegraph.
"He is in a permanent vegetative state and is assisted in breathing by a life support machine," read a court document regarding burial rights.
"The Mandela family have been advised by the medical practitioners that his life support machine should be switched off. Rather than prolonging his suffering, the Mandela family is exploring this option as a very real probability."
Charlene Smith, an authorised biographer of the former anti-apartheid leader said: ""He's basically gone ... He's not there. He's not there."
The document was submitted to a closed hearing last week by a lawyer acting for Mandela's oldest daughter. It is dated June 26 and was leaked to AFP on Thursday (local time).
However, a spokesperson for South African President Jacob Zuma challenged the reports.
"We have reported even today as a result of President Zuma's visit that Madiba (Mandela) remains in a critical but stable condition, and that is based on Mr Zuma going to the hospital and being briefed by the doctors.
"Certainly in that statement, there is no suggestion that he is in a vegetative state,'' Mac Maharaj said.
A later statement from Zuma's office said: "The doctors deny that the former President is in a vegetative state."
There was a possibility lawyers acting for the family in a recent court case over the bodies of three of his children may have exaggerated Mandela’s condition, he said.
In Mandela's hometown, Qunu, on Thursday (local time), the children's bodies were returned to their original resting site following the court order.
Family members and community elders attended a ceremony on the Mandela property that included the singing of hymns. The reburial took place in Qunu, where Mandela grew up and where the former president has said he wants to be buried. Forensic tests earlier confirmed the remains were those of Mandela's children.
Grandson Mandla Mandela moved the bodies to his village of Mvezo - Nelson Mandela's birthplace - in 2011. The two towns are about 25 kilometres apart. Fifteen Mandela family members pursued court action last week to force the grandson to move the bodies back to their original burial site.
Mandla Mandela - the oldest male Mandela heir and a tribal chief - told a news conference on Thursday that "my grandfather like myself would be highly disappointed in what is unravelling."
The bitter family feud comes as Mandela remains in critical condition nearly a month after being hospitalised for a recurring lung infection.
Mlawu Tyatyeka, an expert on the Xhosa culture of Mandela's family, said the court case over the graves was decided quickly because the family knows that Mandela will soon die.
"It's not a case of wishing him to die. It's a case of making sure that by the time he dies, his dying wish has been fulfilled," he said. "We have a belief that should you ignore a dying wish, all bad will befall you."
Mandela was imprisoned for 27 years during white racist rule and was freed in 1990 before being elected president in all-race elections. He won the Nobel Peace Prize along with former President F.W. de Klerk.