QUNU, South Africa - Nelson Mandela's close family gathered Tuesday at his rural homestead to discuss the failing health of the South African anti-apartheid icon who is fighting for his life in hospital.

Messages of support poured in from around the world for the Nobel Peace Prize winner, who spent 27 years behind bars for his struggle under white minority rule and went on to become South Africa's first black president.

Mandela remained unchanged in critical condition Tuesday, the South African presidency said. "We must keep him in our prayers and leave the rest to the Almighty to decide on," Deputy President Kgalema Motlanthe said.

Family members including one of Mandela's daughters and at least two grandchildren were seen gathering for a meeting in the village of Qunu, where the charismatic former leader spent his childhood tending cattle and living in mud-walled huts. The meeting was called "to discuss delicate matters", according to South Africa's SAPA news agency, amid speculation that the location of his possible gravesite was on the agenda.

The 94-year-old's condition appeared to take a significant turn for the worse over the weekend with the presidency announcing on Sunday that he was "critical".

Flowers and messages of support piled up outside the Pretoria hospital where Mandela was admitted on June 8 with a recurring lung problem dating back to his time at the windswept Robben Island prison camp near Cape Town. "He is a man who changed the world," said Vusi Mzimanda, who was among the well-wishers.

"He brings hope to everyone," he said. "I just hope that he will get better and come to us. We don't want to lose him even though we know it's late."

Supporters also released 100 white doves into the air outside the hospital.

"It symbolises that fact that we need to have love as South Africans, we need to have peace in South Africa," said dove breeder Thomas Toutts.

Relatives have been coming to Mandela's bedside in hospital each day as doctors battle to save the moral icon, who was once considered a terrorist by the United States and Britain for his support of violence against the apartheid regime.

Ex-wife Winnie Madikizela-Mandela - herself a figurehead of the anti-apartheid struggle - and his grandchildren visited the hospital on Tuesday.

President Jacob Zuma called on South Africans to respect the Mandela family's "dignity and privacy".

"We must demonstrate our love and appreciation for his leadership during the struggle for liberation and in our first few years of freedom and democracy by living out his legacy and promoting unity, non-racialism, non-sexism and prosperity in our country," Zuma said in a statement.

Messages of goodwill flooded in from overseas, including from the White House, which said its thoughts and prayers were with Mandela.

US President Barack Obama leaves Wednesday on a much-awaited tour of Africa that will take him to South Africa as well as Senegal and Tanzania.

The White House said it was monitoring Mandela's condition and could not yet say whether his ill health would affect the visit.

Obama is unlikely to see Mandela during his visit, South Africa's minister of international relations said.

"President Obama would have loved to see president Mandela, but he is indisposed," said Maite Nkoane Mashebane.

Mandela - who is due to celebrate his 95th birthday on July 18 - has been hospitalised four times since December, and South Africans have been coming to terms with his increasing frailty.

Upon his release from jail in 1990 in one of the defining moments of the 20th century, Mandela negotiated an end to apartheid and won the country's first fully democratic elections.

He served a single term as president, guiding the country away from internecine racial and tribal violence, before taking up a new role as a roving elder statesman and leading AIDS campaigner. He retired from public life in 2004.

The South African government has been criticised following revelations that the military ambulance that carried Mandela to hospital developed engine trouble, resulting in a 40-minute delay until a replacement vehicle arrived.

The presidency said Mandela suffered no harm during the wait for another ambulance to take him from his Johannesburg home to a specialist heart clinic in Pretoria 55 kilometres (30 miles) away.