FILE - In this Tuesday, Dec. 18, 2007 file photo, then Democratic presidential hopeful, Sen. Barack Obama, D-Ill., right, speaks prior to a foreign policy forum as then retired Air Force Gen. Scott Gration, left, looks on in Des Moines, Iowa. The U.S. ambassador to Kenya Scott Gration said Friday, June 29, 2012 that he is leaving his post over differences with Washington on his leadership style, adding that he resigned Monday, June 25, 2012, effective Saturday, July 28, 2012. (AP Photo/Kevin Sanders, File)