Earlier in the day, Turkish Foreign Minister Mevlut Cavusoglu said on the sidelines of the NATO summit in Washington that Turkey would inform US Secretary of State Mike Pompeo and National Security Advisor John Bolton that its purchase of Russian S-400 air defense systems was a "done deal."
Hours after Cavusoglu's statement, US Vice President Mike Pence warned Ankara against purchasing Russian anti-missile systems that Washington considers a threat to US military equipment.
"Turkey must choose. Does it want to remain a critical partner in the most successful military alliance in history or does it want to risk the security of that partnership by making such reckless decisions that undermine our alliance?" Pence said in remarks at a NATO event in Washington.
Russia and Turkey signed a loan agreement for the supply of S-400 air defence systems in 2017. In early March, Turkish President Recep Tayyip Erdogan reaffirmed that the deal with Russia on deliveries of the S-400 air defence systems was completed, and said a new deal on purchases of advanced Russian-made S-500 systems could be possible in future.
A State Department official told Sputnik on Monday that the US government warned Ankara that it could face even more consequences including sanctions for purchasing Russian S-400 systems.