"We proposed to the US to establish a working group led by NATO, but the US rejected our offer," Cavusoglu said, as quoted by the Turkish newspaper Daily Sabah.
US Secretary of State Mike Pompeo called Turkey’s tests of the S-400 anti-aircraft missile and radar systems "concerning" during a press briefing on Tuesday.
The United States has repeatedly objected to Ankara’s purchase of the Russian-made defence system, saying that the weapons system is incompatible with NATO security standards. Ankara insists that the S-400 systems would not pose a threat from the alliance and resisted US pressure to cancel orders.
"We have different opinions but we can continue to talk," Cavusoglu remarked, as quoted by the Turkish newspaper. The article noted that Ankara’s decision to purchase the S-400 systems was a necessary step after protracted negotiations to buy an air defence system from Washington collapsed.
Russia and Turkey initially signed a $2.5 billion deal for the delivery of four S-400 batteries in December 2017. An agreement for a second regiment of S-400 missile systems is expected to be signed in 2020, Russia's Rosoboronexport Director General Alexander Mikheev told Sputnik on Tuesday.
The S-400 deliveries, which have triggered a crisis in Turkey's relations with the United States, started in mid-July. The systems are expected to become fully operational by April 2020, according to Turkish President Recep Tayyip Erdogan.