The U.S. cites concern over Ankara's plans to purchase the Russian S-400 missile defense systems although other NATO countries had previously procured earlier generation S-300 missiles without this conflicting with their membership in the alliance.
Following protracted efforts to purchase air defense systems from the U.S. with no success, Ankara decided in 2017 to purchase the S-400.
The S-300 system, completed in 1978, is designed to defend against short and medium-range air attacks and is considered one of the world's most powerful air defense systems.
Russia sold the S-300 system to 20 countries, including NATO member countries such as Bulgaria, Greece and Slovakia.
The Kardak crisis in the Aegean Sea, which broke out in the final days of 1995 and reached its peak in January 1996, became a turning point in Greece's defense strategy.
Failing to stand its ground against Turkey in its claiming of the Kardak islets, Greece concluded that the proportional arms sales that the U.S. made to both sides of the Aegean (that is, Greece and Turkey) to strike a balance between the two countries could not meet its needs.
The first step Athens took in this regard in 1996 was to sign a deal with Russia for the purchase of S-300 air defense system for deployment on Greek Cypriot soil.
These missiles could not be deployed in southern Cyprus as a result of Turkish pressure, but in 1998 they were deployed on the Greek island of Crete, whose strategic importance has been steadily rising.
Greece signed new agreements with Russia in 1999 and 2004 to purchase TOR-M1 and OSA AKM (SA-8B) medium- and low-altitude air defense systems.
These Russian-made air defense systems are currently an integrated part of the air defense system of Greece -- a NATO nation-- and have also been deployed in Greek Cyprus.
Both missile systems have radar systems that would pose a danger to NATO air forces.
S-300s were initially developed for use against aircraft, but later it became capable of defending against ballistic missiles.
The system is capable of simultaneously tracking 100 targets on radar, locking on to up to six targets at a time and can launch up to 12 rockets.
The U.S. also purchased the Russian-made S-300 air defense system in the past, the New York Times said on Dec. 24, 1994.
The U.S. has secretly purchased one S-300 system to examine the system and develop its own Patriot systems, the report added..
