U.S. Defense Secretary Leon Panetta, right, smiles as he is greeted by U.S. Ambassador to Afghanistan James B. Cunningham, center, and Marine Gen. John R. Allen, left, commander of International Security Assistance Force, upon arriving at Kabul International Airport in Kabul, Afghanistan, Wednesday, Dec. 12, 2012. (AP Photo/Susan Walsh, Pool)

Photo by: Susan Walsh

U.S. Defense Secretary Leon Panetta, right, smiles as he is greeted by U.S. Ambassador to Afghanistan James B. Cunningham, center, and Marine Gen. John R. Allen, left, commander of International Security Assistance Force, upon arriving at Kabul International Airport in Kabul, Afghanistan, Wednesday, Dec. 12, 2012. (AP Photo/Susan Walsh, Pool)