- World powers agree to "cessation of hostilities" and to delivery of immediate aid in Syria
- Aaron Miller: Assad regime, allies have vital interests they are prepared to protect by force
- Washington does not, Miller says, lacking the will, allies or assets on the ground
Aaron David Miller is a vice president and distinguished scholar at the Woodrow Wilson International Center for Scholars and author of "The End of Greatness: Why America Can't Have (and Doesn't Want) Another Great President." Miller was a Middle East negotiator in Democratic and Republican administrations. Follow him on Twitter @aarondmiller2. The opinions expressed in this commentary are his.
(CNN)On Friday, the United States and Russia announced their agreement on a process to deliver humanitarian aid to besieged Syrian cities and to implement a national ceasefire, or even a more temporary cessation of hostilities. This is a stunningly ambitious undertaking -- and it falls somewhere between a long shot and a mission impossible.