US officials advised Turkey to buy the US Patriot missile system rather than the S-400s from Moscow, arguing the Russian system would be incompatible with North Atlantic Treaty Organisation systems and expose the F-35 to possible Russian subterfuge. It is a done deal.
The language used in a letter sent from the United States to Ankara regarding Turkey's removal from the F-35 fighter jet programme does not suit "the spirit of alliance", Turkish Defence Minister Hulusi Akar has said.
Russian Federation and Turkey penned a $2.5-billion contract for the delivery of four battalion sets-worth of S-400s to Ankara in late 2017.
Turkey has criticized the letter from Washington and said it did not live up to the spirit of the North Atlantic Treaty Organisation alliance.
US Acting Secretary of Defense Patrick Shanahan's letter to his counterpart, seen by Reuters, had outlined how Turkey would be pulled out of the F-35 fighter jet program unless Ankara changes course from its plans to purchase a Russian missile defense system.
Turkey, however, emphasized the S-400 would not be integrated into North Atlantic Treaty Organisation systems and would not pose a threat to the alliance.
But Erdogan said Wednesday that his government would hold to account anyone who excluded Turkey from the F-35 program.
Turkish officials have indicated that negotiations on the Patriot proposal are continuing, but have stressed that Ankara would not cancel the S-400 deal for the US-made systems.
Turkey has consistently contested the Greek Cypriot administration's unilateral drilling in the Eastern Mediterranean, saying Turkish Cypriots also have rights to the resources in the area and Ankara has a right to hydrocarbon drilling activities in the region.
Turkey and US flags are seen in this picture illustration taken August 25, 2018. "We haven't suspended any of the maintenance activity", he added.
Ankara has been infuriated by USA support for the YPG, which it considers a terrorist organization and an extension of the outlawed Kurdistan Workers' Party (PKK), which has fought an insurgency in southeast Turkey for more than three decades.