According to Reuters, senior US officials informed a group of journalists and told that Turkey's decision to purchase S-400 would create a national security issue for the NATO. Senior officials noted that Turkey's S-400 decision was not tantamount to it withdrawing from NATO, but that Ankara’s purchase should be viewed as a national security issue, not a merely commercial decision.
One of the senior US officials stated that they continue working on a range of options to ensure Turkey's accession to NATO and bilateral relations not interrupted. “The gravity of the risk to the F-35 both to the United States and to NATO allies is such that the two systems cannot be co-located,” the official said.
Ankara and Washington continue making controversial statements over Turkey's plans to take purchase Russian missile defense system S-400. Turkey's insistence on buying the Russian missiles might trigger a new diplomatic crisis.
While the US officials "warn" Ankara about that the US will impose sanctions if the S-400 deal comes true, Turkish officials respond saying the deal has already been made and the US should be sending Patriots as agreed.
Turkey's President Erdoğan said on Thursday that Ankara could not step back from the agreement with Russia.