Turkish Foreign Minister Mevlut Cavusoglu and his U.S. counterpart Mike Pompeo had a phone conversation on Saturday, in which they discussed the F-35 fighter jet program and S-400 air defense systems issues and Syria, according to Turkish diplomatic sources.
Cavusoglu and Pompeo discussed the F35, S-400 and Syria issues, particularly the Manbij, Idlib and safe zone issues, the sources, who asked not to be named due to restrictions on speaking to media, said.
Following protracted efforts to purchase an air defense system from the U.S. with no success, Ankara signed a contract in 2017 to purchase the S-400s from Russia.
U.S. officials argued the Russian system would be incompatible with NATO systems and expose the F-35s to possible Russian subterfuge.
Turkey, however, emphasized the S-400 would not be integrated into NATO systems and would not pose a threat to the alliance.
It urged the formation of a commission to clarify any technical issues, but the U.S. failed to respond to this proposal.
The U.S. threatened sanctions over the purchase, with Turkey responding that any sanctions would be met in kind.
The delivery of S-400 components began last week and is ongoing, with 14 shipments of related equipment so far have landed in Turkey over the last nine days.
Deliveries are set to continue through April 2020.