Crew members of the U.S. Navy destroyer USS Jason Dunham load supplies while docked in Guantanamo Bay, Cuba, earlier this year. The U.S. and Cuba have restored diplomatic relations, but the U.S. says it remains committed to keeping the base. David Welna/NPR hide caption

itoggle caption David Welna/NPR

The Pentagon's only maximum security prison, at the U.S. Army's Fort Leavenworth in Kansas, is one of the facilities being considered for placement of Guantanamo prisoners deemed too dangerous to release. Julie Denesha/Getty Images hide caption

itoggle caption Julie Denesha/Getty Images

Kurdish rebels in northern Syria walk near the devastated town of Kobani last November. The U.S. bombing campaign helped the Kurds push back the Islamic State from the area. But overall, the U.S. operation against ISIS in Iraq and Syria has shown only limited gains in the past year. Jake Simkin/AP hide caption

itoggle caption Jake Simkin/AP

Captives separated by a fence conduct communal evening prayers at the Camp 6 prison building at the U.S. Naval Base at Guantanamo Bay, Cuba. Walter Michot/Miami Herald/TNS/Landov hide caption

itoggle caption Walter Michot/Miami Herald/TNS/Landov

President Obama hosts leaders of the Gulf Cooperation Council at Camp David, Md., on May 14. The president gave assurances that the U.S. would support its allies in the region concerned over Iran's growing influence. Andrew Harnik/AP hide caption

itoggle caption Andrew Harnik/AP