WASHINGTON — Only one route remains open for international convoys bringing food, water and other aid to over one million Syrians besieged by civil war. Now, officials warn, Russia might try to shut it down or use it as a bargaining chip with world powers in another war, about 1,000 miles away in Ukraine.
Diplomats and experts said closing the corridor, at the Bab al-Hawa border crossing with Turkey, would almost certainly force thousands of…