Nelson Mandela update: critical but stable (VIDEO)

Former South African President Nelson Mandela in 2008.

Nelson Mandela is in critical but stable condition at a hospital in Pretoria, where he was admitted on June 8, South African President Jacob Zuma’s office said on Monday.

The 94-year-old has been receiving treatment for a recurring lung infection.

He was too sick on Saturday to see US President Barack Obama, in South Africa for a few days as part of a three-country African tour.

More from GlobalPost: Obama meets Mandela's family, does not see ailing leader

Instead, Obama had a private meeting with Mandela’s daughters Makaziwe Mandela and Zindzi Mandela Hlongwane and several of his grandchildren in Johannesburg. The US president also spoke to Mandela's wife, Graca Machel, by phone.

Mandela did receive a visit from his former wife, Winnie Madikizela-Mandela, on Sunday, the South African Press Association reported. "It is extremely painful to see him going through what he's going through now. But it's God's wish," Winnie Mandela told UK network ITV News in an interview, according to CNN.

Zuma urged South Africans to channel their affection for their former leader into positive action. “We remind all South Africans to begin planning for Madiba’s birthday on the 18th of July,” Zuma said in a statement. “We must all be able to do something good for humanity on this day, in tribute to our former President.”