Sources disclosed Monday that veteran U.S. diplomat Ryan Crocker is expected to step down from his position as special envoy to Afghanistan as early as this month. President Obama addressed the withdrawal of U.S. forces in the war-torn country Monday to close the NATO summit, saying that “real challenges” remain through much of the region. Crocker is said to be widely respected for his work in Kabul and the reason for his departure was not immediately clear. The president is reportedly considering Deputy Ambassador James Cunningham as Crocker’s replacement. Crocker came out of retirement in July 2011 to fill the post and participated in NATO summit talks about the country’s future.