Former South African president Nelson Mandela remains in critical condition at a hospital in Pretoria, where he's being treated for a lung infection, the presidency said Monday.
At a press briefing Monday morning, President Jacob Zuma said doctors were doing everything they could for the 94-year-old statesman.
It was announced Sunday night that Mandela's condition had worsened, two weeks since he was hospitalized. Previously, authorities had described his condition as serious but stable.
Zuma broke the news after visiting Mandela in the hospital Sunday evening. Mandela was asleep at the time, Zuma said, but doctors told him "that the former president's condition had become critical over the past 24 hours."
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The anti-apartheid icon has been hospitalized in Pretoria since June 8 for a recurring lung infection.
On Monday, Zuma asked South Africans to pray for their beloved Madiba, the clan name often affectionately used for Mandela.
"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," African National Congress spokesman Jackson Mthembu said in a statement.
"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."
US President Barack Obama is due to arrive in South Africa on Friday on a scheduled visit. Zuma said Monday that he expected the trip to go ahead as planned, regardless of Mandela's long-running health problems.
Later Monday, White House spokesman Jay Carney refused to speculate on how Mandela's health would impact Obama's trip, only saying that Obama "continues to look forward to his trip."
"The president obviously has long seen Nelson Mandela as one of his personal heroes, and I think he's not alone in that in this country and around the world," said Carney.
Mandela has become increasingly frail over the years and has not appeared in public since South Africa hosted the World Cup in 2010.
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The Nobel Peace Prize winner's history of lung problems dates back to his years in prison on Robben Island, where he contracted tuberculosis.
He spent spent 27 years as a prisoner of the South African government under South Africa's last white president, F.W. de Clerk.
He then embarked on a "long walk to freedom" which saw him crowned South Africa's first black president, a role he stepped down from in 1999 after one term in office.
Zuma reiterated Sunday that Mandela's health was not compromised when the ambulance that was bringing him to the hospital on June 8 broke down.
"There were seven doctors in the convoy who were in full control of the situation throughout the period. He had expert medical care," he said, according to ABC News. "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, who turns 95 on July 18, was forced to wait for a second ambulance after the first one broke down, the South African government admitted Saturday.
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