Greece, a NATO member, has been in possession of the advanced Russian-made systems since the late 1990s and in a defiant show of independence towards Troika, is now negotiating with Russia for the purchase of additional missiles and for their maintenance.

As Reuters reports,

Greece is negotiating with Russia for the purchase of missiles for its S-300 anti-missile systems and for their maintenance, Russia's RIA news agency quoted Greek Defense Minister Panos Kammenos as saying on Wednesday.

 The report followed a visit by Greek Prime Minister Alexis Tsipras last week to Moscow, where he won pledges of Russian moral support and long-term cooperation but no fresh funds to help avert bankruptcy for his heavily indebted nation.

 NATO member Greece has been in possession of the Russian-made S-300 air defense systems since the late 1990s.