A former banker now with Treasury Department made a secretive trip, warning countries to end flights and cut off banks A top U.S. Treasury Department official hopscotched across the Middle East and Europe this month with a warning to Iran’s trading partners: You either trade with Tehran or Washington. The commercial strongarming is working.In recent days, Iran has seen its airlines cut off from critical regional routes and its top commercial bank stopped from transacting in the United Arab Emirates and Turkey, both actions that came on top of longstanding sanctions and the continuing U.S. naval blockade.A growing distrust of...