South African president Jacob Zuma urged the nation to pray for Mr Mandela as hopes the 94-year-old would make a recovery began to fade.
Mr Zuma described the ailing icon of the anti-apartheid movement as the “father of democracy,” and said doctors were doing everything possible to make him feel comfortable.
South Africa’s first black president was taken to hospital in Pretoria earlier this month for the third time this year, with a lung infection. He has been under care at the Mediclinic hospital for 17 days.
On Sunday night, it was revealed that his condition had deteriorated and he was now in a critical condition.
Mr Mandela’s daughter Makaziwe said the family was taking each day as it came and enjoying as much time as possible with a man who, to them, is a father, grandfather or great-grandfather.
“He is at peace with himself,” she said. “He has given so much to the world. I believe he is at peace.”
Ms Mandela, the former statesman’s eldest daughter with his first wife Evelyn, said he was being treated with “the best medicine in the world” but that the family had accepted he would not be with them much longer.
“All we do every day is take one day at a time and pray to the good Lord,” she said. “All I pray for as a daughter is that the transition is smooth.”
Other family members continued with their visits to Mr Mandela yesterday, including his former wife, Winnie Madikizela-Mandela.
South Africans adopted a mood of sombre resignation.
“If it’s his time to go, he can go. I wish God can look after him,” said nurse Petunia Mafuyeka, as she headed to work in Johannesburg.
“We will miss him very much. He fought for us to give us freedom. We will remember him every day. ”
There was some concern among the public about doctors trying to prolong Mr Mandela’s life.
“I’m worried that they’re keeping him alive. I feel they should let him go,” said Doris Lekalakala, a claims manager. “The man is old. Let nature take its course. He must just rest.”
At a press briefing yesterday, Mr Zuma said Mr Mandela was asleep when he visited his bedside, and stressed that he was unable to give further details about his condition, explaining: “I’m not a doctor to describe the condition, to say how critical.
“All of us in the country must accept that Madiba [Mr Mandela’s clan name] is now old. As he ages, his health will trouble him.
“Madiba is critical in the hospital, and this is the father of democracy. This is the man who fought and sacrificed his life to stay in prison, the longest-serving prisoner in South Africa.”
US president Barack Obama is due to visit South Africa this week as part of a three-country tour but Mr Zuma said Mr Mandela’s worsening state of health should not affect the trip.
“Nothing is going to stop the visit because Madiba is sick,” he said.