Nelson Mandela remained in critical condition for a second straight day, South African President Jacob Zuma said Monday.

“All of us in the country should accept the fact that Madiba is now old,” Zuma told reporters in Johannesburg, referring to Mandela, 94, by his clan name. “As he ages, his health will . . . trouble him, and I think what we need to do as a country is to pray for him.”

The anti-apartheid icon has been hospitalized in the capital, Pretoria, for a recurring lung infection since June 8. Zuma provided few details Monday about Mandela’s condition, which deteriorated to a critical state over the weekend, and doctors were not made available to discuss his health. Zuma described the former South African president as being asleep when he visited him Sunday evening.

Mandela’s hospitalization, Zuma said, is not expected to affect an official visit Friday by President Obama, who this week embarks on his second and most substantial presidential trip to Africa. In addition to South Africa, Obama will stop in Senegal and Tanzania.

Mandela has been hospitalized four times since December. As of Saturday, the South African government has characterized his condition as “serious but stable.”

On Monday, a somber mood pervaded the country. Both the ruling African National Congress party (ANC) and its main rival, the Democratic Alliance party, issued statements asking South Africans to keep Mandela in their thoughts and prayers.

In an interview with CNN, Mandela’s daughter, Makaziwe Mandela, asked that the family’s privacy be respected.

“This is in a sense quality and sacred time for us, and I would expect the world to really back off and leave us alone,” she said.

South Africa’s apartheid regime imprisoned Mandela for 27 years for his crucial role in the struggle against white rule before releasing him in 1990 as national and international pressure against the government’s brutal racial segregation mounted. He contracted tuberculosis in the 1980s while working at the prison quarry on Robben Island, which is believed to be the source of his current lung problems.

In 1993, Mandela shared the Nobel Peace Prize with F.W. de Klerk, who was the last president during white rule and began dismantling apartheid. Mandela became the nation’s first black president following South Africa’s first multiracial elections in 1994, won by the ANC.

Mandela has not been seen in public since the 2010 World Cup soccer tournament, which was held in South Africa.

Monday marked the 18th anniversary of a pivotal moment in Mandela’s efforts to bridge South Africa’s racial divide: At the 1995 Rugby World Cup final in Johannesburg, Mandela united South Africans in support of the Springboks, the national team that was once all-white and hated by blacks as a vehicle of the apartheid regime.

Over the weekend, the South African government came under fire after reports that an ambulance transporting Mandela to the hospital on June 8 broke down and that Mandela suffered cardiac arrest during the episode. Another ambulance arrived to take Mandela to Pretoria, a roughly 45-minute drive from Mandela’s home in an upscale Johannesburg neighborhood.

On Sunday, Zuma confirmed that the first ambulance had broken down but dismissed media reports of the cardiac arrest as false.

“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.