Air Force One landed at a military airbase near Pretoria on Friday evening, the second stop after Senegal, in Obama´s three-country tour of Africa. During his stay, he is scheduled to meet President Jacob Zuma. He is also expected to visit Robben Island, where Mr Mandela was imprisoned for 18 years.
However President Obama said he did not expect to see former President Nelson Mandela, who is critically ill in hospital: "The last thing I want to do is to be in any way obtrusive at a time when the family is concerned with Nelson Mandela's condition…I think the main message we'll want to deliver is not directly to him, but to his family - is simply profound gratitude for his leadership all these years, and that the thoughts and prayers of the American people are with him, his family and his country."
President Obama met Mr Mandela in 2005 when he was still a US senator. Both men became the first black presidents of their nations and have received the Nobel Peace Prize.
The US president has described Mr Mandela as a "hero for the world", whose "legacy will linger on through the ages", and who had inspired his own activism as a student.
Michelle Obama met with former President Nelson Mandela at his home in Houghton, South Africa in 2011.
Official White House Photo by Samantha Appleton
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