U.S. President Barack Obama, right, walks to Air Force One during a departure ceremony with Senegalese President Macky Sall on Friday, June 28, 2013, in Dakar, Senegal. Obama is visiting Senegal, South Africa, and Tanzania on a week long trip. (AP Photo/Evan Vucci)
June 28, 2013 6:24:30 AM PDT
NEDRA PICKLER Associated Press
ABOARD AIR FORCE ONE (AP) - June 28, 2013 --
President Barack Obama, in the midst of a historic tour of Africa, says he isn't certain about whether he'll be able to visit gravely ill Nelson Mandela when he arrives in South Africa.