The United States is talking to Turkey about its concern over Ankara's decision to co-produce a long-range air and missile defence system with a Chinese firm under US sanctions, US Ambassador Francis Ricciardone said on Thursday."We are very concerned about the prospective deal with the sanctioned Chinese firm. Yes this is a commercial decision, it is Turkey's sovereign right, but we are concerned about what it means for allied air defence," Ricciardone told reporters.