FILE - In this April1 14, 2018, file photo, then-Marine Lt. Gen. Kenneth "Frank" McKenzie speaks during a media availability at the Pentagon in Washington.   In a blunt assessment Tuesday, Gen. Frank McKenzie, head of U.S. Central Command, told Congress it will be extremely difficult but not impossible for the U.S. to find, track and take out counterterrorism threats in Afghanistan once all American troops are withdrawn.   (AP Photo/Alex Brandon, File)
'When you deal with a security issue or a malign actor or nation, you are always better when the response is a collective response from a group of nations that come together,' Gen McKenzie said. (FileShow more

US commander: some troops to remain in region after Afghanistan withdrawal