U.S. Secretary of State Mike Pompeo has expressed "the United States' disappointment" in a phone call with Turkish Foreign Minister Mevlut Cavusoglu over Ankara's purchase of a Russian missile-defense system, the State Department says.
The recent arrival in Turkey of the first components of the Russian S-400 surface-to-air missile system has strained relations and threatens billions in defense manufacturing and cooperation between the two NATO allies.
The call appeared to have been the most senior direct contact between Ankara and Washington since reports said Turkey had received the first several shipments of the system on July 12 -13.
U.S. and NATO military officials have long opposed Turkey's involvement with the S-400, saying it is incompatible with the transatlantic military alliance's systems and would endanger NATO warplanes.
Washington said a purchase would automatically require it to set sanctions and said it would block Turkey's order of more than 100 F-35 stealth fighters.
The Pentagon announced the S-400 deal would prompt the exclusion of Turkey from an F-35 manufacturing program.
It is unclear whether the United States will impose sanctions on Ankara, which has boosted relations with NATO critic Russia as Turkish President Recep Tayyip Erdogan has tightened his power over the country's media and its 80 million people in recent years, particularly since a deadly coup seeking to sideline Erdogan was defeated in 2016.
In Washington, Republican and Democratic lawmakers this week tried to make the case for punishing Turkey, saying President Donald Trump should proceed with sanctions based on a U.S. law prescribing penalties for doing business with the Russian military.
Turkey makes numerous components for the F-35 and the United States will have to find alternative suppliers, reportedly adding at least $500 million to the cost of production.
News of Turkish talks to buy S-400 systems emerged in late 2016 and a deal was signed less than a year later, potentially putting Turkey on a rocky path its NATO allies.
U.S. President Donald Trump said last week it was still unclear whether Washington would slap sanctions on Turkey but said that "we're looking at it. Very, very difficult situation for a lot of reasons."
The United States has pledged continued cooperation with Turkey in common defense aims, "mindful of constraints" brought on by the S-400 purchase.
In its statement, the State Department said the U.S. and Turkish foreign ministers also discussed the situation in Syria and the U.S. "commitment to addressing Turkish security concerns along the Turkey-Syria border," "while also reiterating the U.S. government's obligation to ensure the protection of local partners working with the United States and the Global Coalition to Defeat ISIS," a reference to the militant group Islamic State.
Pompeo also "expressed his condolences...regarding the July 17 attack in Erbil, Iraq, which resulted in the death of a Turkish diplomat."