President Barack Obama walks down the stairs of Air Force One as he arrives at Kenyatta International Airport, in Nairobi, Kenya. Obama arrived to begin a two-nation tour of Africa focused on deepening economic and security partnerships with the continentPresident Barack Obama hugs Joan Wamaitha, 8, who presented him with flowers, as he arrives at Kenyatta International Airport, in Nairobi, Kenya. Obama is traveling on a two-nation African tour where he will become the the first sitting U.S. president toU.S. President Barack Obama waves after being greeted by Kenya's President Uhuru Kenyatta, right, on his arrival at the Jomo Kenyatta International Airport in Nairobi, Kenya | APKenyan President Uhuru Kenyatta, left, watches as President Barack Obama signs a guest book after arriving at Kenyatta International Airport, in Nairobi, Kenya. Obama is traveling on a two-nation African tour where he becomes the the first sitting U.S. prKenyan President Uhuru Kenyatta, left, talks with President Barack Obama as he signs a guest book after arriving at Kenyatta International Airport, in Nairobi. Obama is traveling on a two-nation African tour where he will become the the first sitting U.S.U.S. President Barack Obama is hugged by his half-sister Auma Obama, left, accompanied by Kenya's President Uhuru Kenyatta, right, as he arrives at the Jomo Kenyatta International Airport in Nairobi, Kenya | APKenyan President Uhuru Kenyatta, right, watches as President Barack Obama, center, hugs his half-sister, Auma Obama, after he arrived at Kenyatta International Airport, in Nairobi, Kenya. Obama is traveling on a two-nation African tour where he will becomPresident Barack Obama hugs his half-sister Auma Obama as he arrives at the Jomo Kenyatta International Airport in Nairobi, Kenya. Obama began his first visit to Kenya as U.S. president Friday | AP