The Pentagon has indefinitely postponed a press briefing on Turkey accepting delivery of an advanced Russian missile defense system. The briefing was supposed to take place earlier on Friday, July 12, says Reuters. The Pentagon said Acting U.S. Defense Secretary Mark Esper had spoken with his Turkish counterpart. No details were provided regarding their discussion. The first shipment of the Russian-made S-400 air defense missile system arrived in Ankara at the Murted Air Base on Friday.