If Turkey decided to buy the S-400 air defense systems from Russia, it would be a cause for concern in the United States, Chairman of the US Joint Chiefs of Staff Joseph Dunford said on Sunday, Sputnik reports.
"There was a media report that was incorrect, they have not bought the S-400 air defense system from Russia. That would be a concern, were they to do that, but they have not done that," Dunford said at the Aspen Security Forum in Colorado.
