Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. Ankara Defies Washington Over Russian Missiles Dorian Jones ISTANBUL - Turkey and the United States are seemingly closer to a collision course as Turkish media report Ankara testing a Russian anti-aircraft weapon system, despite threats of Washington sanctions. Turkish F-16 jets flew low Monday across the Turkish capital, in a two-day exercise reportedly to test the radar system newly acquired Russian S-400 missile system. Ankara's purchase of the S-400s is a significant point of tension with Washington, which claims the system poses a threat to NATO's defenses. "There is room for Turkey to come back to the table. They know that to make this work, they need to either destroy or return or somehow get rid of the S-400," a senior State Department official told reporters at a briefing Wednesday. The official added that sanctions could follow if Ankara went ahead and activated the system. Ankara's purchase of the S-400 system violated U.S. Congress's Countering America's Adversaries Through Sanctions Act (CAATSA). .