WASHINGTON, DC - AUGUST 03: U.S. President Barack Obama addresses the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 1000 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

WASHINGTON, DC - AUGUST 03: Mandela Washington Fellows listen to U.S. President Barack Obama address the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 1000 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

WASHINGTON, DC - AUGUST 03: A participant in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders poses with a Nigerian flang before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

U.S. President Barack Obama answers a question as he and Singapore's Prime Minister Lee Hsien Loong hold a joint news conference at the White House in Washington, U.S. August 2, 2016. REUTERS/Jonathan Ernst

U.S. President Barack Obama and first lady Michelle Obama host a state dinner for Singapore Prime Minister Lee Hsien Loong and his wife Mrs. Lee Hsien Loong to the White House in Washington U.S., August 2, 2016. REUTERS/Mary F. Calvert

WASHINGTON, DC - AUGUST 03: Participants in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders pose for photographs before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

WASHINGTON, DC - AUGUST 03: Participants in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders use a variety of mobile devices, including tablets and phones, before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)

WASHINGTON, DC - AUGUST 03: Participants in the Presidential Summit of the Mandela Washington Fellowship for Young African Leaders make photographs before a town hall event at the Omni Shoreham Hotel August 3, 2016 in Washington, DC. As part of Obama's Young African Leaders Initiative, the summit brought together 500 leaders, ages 25-35, from across Africa to the U.S. for 6 weeks of leadership training and mentoring at twenty universities and colleges to 'spur growth and prosperity, strengthen democratic governance, and enhance peace and security across Africa.' (Photo by Chip Somodevilla/Getty Images)