Afghan National Security Adviser Mohammad Hanif Atmar (right) and U.S. Ambassador to Afghanistan James Cunningham exchange documents after signing the Bilateral Security Agreement, with Afghan President Ashraf Ghani (rear, left) and Chief Executive Abdullah Abdullah in the background. Jawad Jalali/EPA/Landov hide caption

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Afghan presidential candidates Abdullah Abdullah, left, and Ashraf Ghani Ahmadzai shake hands after signing a power-sharing pact in Kabul Sunday. The first vote in the election was held in April; a runoff followed in June. Wakil Kohsar/AFP/Getty Images hide caption

itoggle caption Wakil Kohsar/AFP/Getty Images

Afghan delegates to the Loya Jirga, or grand assembly, listen to Afghan President Hamid Karzai on Thursday. Some 2,500 elders and community leaders have gathered in Kabul to discuss a U.S.-Afghan security agreement that would define the role of U.S. troops after the combat mission ends next year. S. Sabawoon/EPA/Landov hide caption

itoggle caption S. Sabawoon/EPA/Landov

A member of the Afghan Loya Jirga listens as the more than 2,000 elders begin debating a proposed U.S.-Afghan security pact on Thursday in Kabul. Massoud Hossaini /AFP/Getty Images hide caption

itoggle caption Massoud Hossaini /AFP/Getty Images