Speaking at a news conference in Pretoria, alongside South African President Jacob Zuma, Obama also said the thoughts of Americans were with former leader Nelson Mandela, who remains in a critical condition in hospital.
Obama and Zuma appeared at the Union Buildings that house government offices and the site of Mandela's 1994 inauguration as the country's first black president after 27 years behind bars for his activism.
Ninety four year old Mandela has been in a nearby hospital for three weeks after being admitted with a lung infection.
Obama referred to Mandela by his clan name as he praised South Africa's historic integration from white racist rule as a shining beacon for the world.
- South Africa