South Africans adopted a mood of sombre resignation on Monday to the inevitability of saying goodbye to former president Nelson Mandela after the 94-year-old anti-apartheid leader's condition in hospital deteriorated to critical.

Madiba, as he is affectionately known, is revered among most of South Africa's 53 million people as the architect of the 1994 transition to multi-racial democracy after three centuries of white domination.

However, his latest hospitalisation - his fourth in six months - has reinforced a realisation that the father of the post-apartheid 'Rainbow Nation' will not be around for ever.

President Jacob Zuma, who visited Mandela late on Sunday with African National Congress (ANC) Deputy President Cyril Ramaphosa, reflected the national mood when he told a news conference that Mandela remained critical.

"All of us in the country must accept that Madiba is now old. As he ages, his health will trouble him," Zuma said, declining to give specific details about Mandela's medical condition or other information from his hospital visit.

"Given the hour, he was already asleep. We saw him, looked at him and then we had a bit of a discussion with the doctors and his wife," Zuma said. "I don't think I'm a position to give further details. I'm not a doctor."

U.S. President Barack Obama is due to visit South Africa this week as part of a three-country Africa tour but Zuma said Mandela's worsening state of health should not affect the trip.

"Nothing is going to stop the visit because Madiba is sick," Zuma said.

"WE WILL MISS HIM"

Mandela's deterioration this weekend, two weeks after being admitted in a serious but stable condition with a lung infection, has caused a perceptible switch in mood from prayers for recovery to preparations for a fond farewell.

"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. When he goes I will cry."

There was some concern among the public about doctors trying to prolong the life of South Africa's first black president, one of the 20th Century's most influential figures.

"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."

Since stepping down in 1999 after one term as president, Mandela has stayed out of active politics in a country with the continent's biggest and most important economy. His passing is expected to have little political impact.

His last public appearance was waving to fans from the back of a golf cart before the final of the soccer World Cup in Johannesburg's Soccer City stadium in July 2010.

During his retirement, he has divided his time between his home in the wealthy Johannesburg suburb of Houghton, and Qunu, the village in the poor Eastern Cape province where he was born.

The public's last glimpse of him was a brief clip aired by state television in April during a visit to his home by Zuma and other senior ANC officials.

At the time, the 101-year-old liberation movement, which led the fight against white-minority rule, assured the public Mandela was "in good shape", although the footage showed a thin and frail old man sitting expressionless in an armchair. – Reuters