The US believes it is possible that Turkey will decide not to buy the Russian S-400 systems, AFP reported referring to high-ranking official.
When asked if Turkey could eventually change its opinion on the S-400, US Air Force Secretary Heather Wilson noted that this is possible
Diplomats are continuing to work on this, she said, repeating that the S-400s are incompatible with the F-35 fighter jets.
The United States suspended the F-35 production program with Turkey. The US law provides for sanctions against any country entering into transactions with Russian arms supply companies.
Two aircraft were delivered to Turkey in June 2018, but officially remain at the US Air Force base near Phoenix, Arizona, so that Turkish pilots can train on them.