Condemning the US threat to eliminate Turkey from a programme on creating F-35 multi-role fighters over its deal to buy Russian S-400 defence system, Kremlin on Wednesday said such ultimatums by Washington is "unacceptable".
"We consider such ultimatums to be unacceptable and we are going on the many statements made by representatives of Turkey's leadership - headed by President [Recep Tayyip] Erdogan - that the S-400 deal is already complete and will be implemented," Al Jazeera quoted Kremlin spokesman Dmitry Peskov as saying.
This comes hours after Turkey said it is preparing for potential US sanctions over the purchase of Russian missile system.
Earlier Pentagon spokesperson Eric Pahon said that the US considers Russia deal with Turkey as a "strategic trick" of Moscow to disconnect Ankara from its western allies.
However, Turkey has indicated that it would not go back on its deal, regardless of the US decision. "Turkey could cooperate with any other country if the US refused to supply F-35 fighters," said Turkish Foreign Minister Mevlut Cavusoglu.
The development would further strain the already fragile US-Turkey relations.
Russia and Turkey signed a deal for S-400 in 2017 after engaging in hectic negotiations for a year. Reportedly, Turkey has already transferred the advance payment.