US officials have warned Turkey not to purchase Russian-made S-400 missiles, saying it would pose a security threat to members states of the North Atlantic Alliance (NATO).

AVA- Unidentified senior US officials, who spoke to a select group of journalist on condition of anonymity on Thursday, said Ankara’s purchase of the S-400 was tantamount to a threat to NATO member states.
Reuters news agency said the unnamed US state officials had warned Turkey against the purchase of the F-35 aircraft, saying the deal would be cancelled if Ankara went through with the purchase of the Russian S-400 missile system.
US officials told reporters that F-35 fighter jets cannot be deployed alongside the Russian-made systems.
Turkey has pointed out that will not retreat from its decision to purchase the Russian-made missile system.
Earlier, Moscow said it will install the Russian-made S-400 missile system in October.
Turkish officials have said that they would not give in to pressure by US-led NATO forces, insisting that the instalment of  the S-400 system would go ahead as planned.
Turkish Vice President Fuat Oktay said earlier this month that Ankara’s decision to buy S-400 air defense missile systems will not be stopped despite strong opposition from Washington and warnings that it should not buy the anti-aircraft platform.
“Turkey does what is necessary for its own interests regarding the S-400 missile defense system, it takes own decision and choice,” Oktay insisted, adding that Ankara will not renege on its agreement with Russia.
Oktay’s remarks came a day after Turkish President Recep Tayyip Erdogan said Ankara would not retreat from buying the S-400 missile defense systems from Russia, adding that Ankara may subsequently also look into buying S-500 systems.
Meanwhile, Turkey has asked Russia to strengthen its air defense systems after Washington’s 2015 decision to withdraw its Patriot surface-to-air missile system from Turkish borders.
Ties between Turkey and US-led NATO further deteriorated after Washington began showing support to Kurdish groups opposed to Ankara.
Turkey has asked US officials to extradite Fethullah Gulen, a powerful Turkish opposition figure who lives in the US. Ankara accuses Gulen, a former ally of Erdogan, of masterminding the July 2016 coup attempt against the Turkish president.