Nelson Mandela's condition in a Pretoria hospital remains critical for a second straight day today, says South Africa's president.
President Jacob Zuma described the stricken anti-apartheid hero as being "asleep" when he visited Mandela on Sunday evening (local time).
Zuma told at least 60 foreign and South African journalists that doctors were doing everything possible to ensure the 94-year-old's wellbeing and comfort on his 17th day in the hospital.
The president repeated some of the content of a presidential statement issued on Sunday and refused to give any details about Mandela's condition, saying: "I'm not a doctor."
"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. He is one of those who has contributed to democracy," Zuma said, using Mandela's clan name.
"All of us in the country should accept the fact that Madiba is now old. As he ages, his health will ... trouble him and I think what we need to do as a country is to pray for him."
Zuma, who in the past has given an overly sunny view of Mandela's health, briefly described his visit to the hospital in the capital and seeing Mandela.
"It was late, he was already asleep," Zuma said.
"And we then had a bit of a discussion with the doctors as well as his wife, Graca Machel, and we left."
Mandela, who became South Africa's first black president after the end of apartheid in 1994, was hospitalised on June 8 for what the government said was a recurring lung infection.
This is his fourth hospitalisation since December.
In Sunday's statement, Zuma also discussed the government's acknowledgement a day earlier that an ambulance carrying Mandela to the Pretoria hospital two weeks ago had engine trouble, requiring the former president to be transferred to another ambulance for his journey.
Pretoria, South Africa's capital, lies about 50 kilometres from Johannesburg, where Mandela has been living.
"There were seven doctors in the convoy who were in full control of the situation throughout the period. He had expert medical care," Zuma said.
"The fully equipped military ICU ambulance had a full complement of specialist medical staff including intensive care specialists and ICU nurses.
"The doctors also dismissed the media reports that Madiba suffered cardiac arrest. There is no truth at all in that report."
Mandela, a Nobel Peace Prize laureate, is seen by many around the world as a symbol of peace and reconciliation.
He was jailed for 27 years under white racist rule and was released 23 years ago, in 1990.
He then played a leading role in steering the divided country from the apartheid era to an all-race democracy, becoming South Africa's first black president in all-race elections in 1994.
Zuma appealed to South Africans and the international community to pray for the ailing ex-president, his family and the medical team attending to him.
The ruling party expressed concern about the deterioration in Mandela's health.
"We welcome the work being done by the presidency to ensure that South Africans and people of the world are kept informed on the state of Madiba's health," the party said.
"The African National Congress joins the presidency in calling upon all of us to keep president Mandela, his family and his medical team in our thoughts and prayers during this trying time."
In Washington, the White House National Security Council spokeswoman noted the latest reports from the South African government about Mandela's worsening condition.
"Our thoughts and prayers are with him, his family and the people of South Africa," said spokeswoman Caitlin Hayden.
Prior to Zuma's statement, reports from the government, former president Thabo Mbeki and a grandson of Mandela had indicated that the health of Mandela was improving, even though he has been in the hospital for treatment several times in recent months.
In the days following his latest hospitalisation, Zuma's office described his condition as serious but stable. Family members have been seen making daily visits to the hospital where Mandela is being treated.
Mandela, who has become increasingly frail in recent years, last made a public appearance at the 2010 World Cup football tournament, which was hosted by South Africa.
He did not deliver an address and was bundled against the cold in a stadium full of fans.
On April 29, state television broadcast footage of a visit by Zuma and other leaders of the African National Congress to Mandela's home.
Zuma said at the time that Mandela was in good shape, but the footage - the first public images of Mandela in nearly a year - showed him silent and unresponsive, even when Zuma tried to hold his hand.
Between hospital stays in recent months, Mandela has been staying at his home in the Johannesburg neighbourhood of Houghton, where he has received what the government described as "home-based high care" by a medical team.
On April 6, he was discharged from a hospital after treatment for pneumonia, which included a procedure in which doctors drained fluid from his lung area.
Mandela has been vulnerable to respiratory problems since contracting tuberculosis during his imprisonment under apartheid. Most of those years were spent on Robben Island, a forbidding outpost off the coast of Cape Town.