Nelson Mandela is on his deathbed, his daughter Makaziwe Mandela has said.
Mandela, 95, was discharged from hospital in September after spending months in a critical condition with a lung infection.
She told South Africa's national broadcaster SABC that Mandela was "still with us, strong and courageous".
"Even for a lack of a better word... on his deathbed he is teaching us lessons - lessons in patience, in love, lessons of tolerance," she said.
"Every moment I get with him I'm amazed. There are times where I have to pinch myself that I come from this man who is a fighter even though you can see he is struggling, but fighting spirit is still there with him."
Her announcement came as Jacob Zuma postponed receiving a state trip from Kazakhstan. There was no official link made between the cancellation and the fears over Mandela's health.
"The State visit by His Excellency President Nursultan Nazarbayey of the Republic of Kazakhstan has been postponed," said the office.
"A new date for the state visit will be communicated at a later stage."
Mandela has been treated at home after spending three months in hospital in Pretoria.
He was described as being in a critical condition and was on a life support machine.
Earlier this month, Makaziwe Mandela said that her father had a "strong spirit" despite his illness.
Speaking at the launch of the Nelson Mandela Opus in Johannesburg, she said: "That spirit is still very, very strong, even if he is sick on his bed. The story of Tata's life has to be repeated and told over and over again, so we don't forget who we are."
Her latest comments came ahead of the UK release of Nelson Mandela: Long Walk to Freedom, which chronicles the former president's life.