In this photo provided by Mouaz Moustafa and the Syrian Emergency Task Force, Sen. John McCain, accompanied by Moustafa (right) visits rebels in Syria on Monday. McCain, who slipped into the country for a surprise visit, favors providing arms to rebel forces in Syria. Mouaz Moustafa/AP hide caption

itoggle caption Mouaz Moustafa/AP

The gray line in the upper left comes from an aerial view of Afghanistan's crucial Highway 1, the main route between Kabul and Kandahar, the two biggest cities. U.S. forces are still working to secure the route which runs through lush farm valleys and the high desert terrain. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

Waliur Rehman, who was reportedly killed Wednesday in Pakistan. U.S. State Dept. hide caption

itoggle caption U.S. State Dept.

U.S. Army Sgt. Michael Johnson trains at Bagram Air Field for the Memorial Day Murphy, a CrossFit workout honoring a Navy SEAL killed in Afghanistan in 2005. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

A wounded Afghan police officer is helped from the scene of Friday's explosion and gunfire in Kabul. Omar Sobhani /Reuters /Landov hide caption

itoggle caption Omar Sobhani /Reuters /Landov

A technician shapes a cast mold for a prosthetic limb at the Red Cross orthopedic clinic in Kabul. The clinic produces about 2,000 prosthetic limbs each year. Sean Carberry/NPR hide caption

itoggle caption Sean Carberry/NPR

An Afghan worker helps excavate part of the mountaintop copper works above the ancient city at Mes Aynak in February. Afghanistan is believed to be sitting on massive mineral and metal deposits. But many obstacles have prevented large-scale mining from getting underway. Matthew C. Rains/MCT/Landov hide caption

itoggle caption Matthew C. Rains/MCT/Landov

The scene Thursday in Kabul, Afghanistan, after a suicide bomber attacked a NATO convoy. Zhao Yishen /Xinhua /Landov hide caption

itoggle caption Zhao Yishen /Xinhua /Landov

Afghan and U.S. officials attend the closing ceremony for the Paktia provincial reconstruction team on April 9 in eastern Afghanistan. NATO created more than 20 teams to help the Afghans rebuild. But now the U.S. teams are winding down their activities. Sean Carberry/NPR hide caption

itoggle caption Sean Carberry/NPR