President Recep Tayyip Erdoğan on Wednesday indicated that Turkey went ahead with the purchase of Russia's S-400 missile system because it was tired of waiting for another supplier.
The deal has caused concern among Turkey's NATO allies as the Russian air defense system is incompatible with the air defenses of other NATO members.
"They went crazy just because we made the S-400 deal," Erdoğan told a meeting of city mayors from his ruling party in Ankara.
"What are we supposed to do? Wait for you? We are taking security measures and will continue to do so."
Earlier this week, Erdoğan said the first payment for the S-400 had been made. The total value of the deal is believed to be around $2.5 billion.
Vladimir Kojin, an aide to Russian President Vladimir Putin, confirmed on Tuesday that a contract had been signed.
"I can merely guarantee that all of the decisions made under this contract strictly agree with our strategic interests," he told the TASS news agency.
The compatibility of the S-400 system is the main concern of NATO.
PATRIOT WITHDRAWAL
"We have relayed our concerns to Turkish officials regarding the potential purchase of the S-400," Pentagon spokesman Johnny Michael told U.S. broadcaster CNBC in a statement on Tuesday.
"A NATO inter-operable missile defense system remains the best option to defend Turkey from the full range of threats in the region."
In March, then Defense Minister Fikri Işık said Turkey had looked to buy a missile system from one of its NATO partners but could not reach agreement on sharing technology or a price.
In 2013, Turkey selected China Precision Machinery Import-Export Corporation for a long-range air defense system but later scrapped the deal under pressure from NATO. Two years later, NATO Patriot missile batteries were withdrawn from Turkey.
In recent years, Turkey has sought to build its domestic defense industry to reduce reliance on foreign suppliers.
The S-400 is Russia's most advanced long-range anti-aircraft missile system and can carry three types of missiles capable of destroying targets including ballistic and cruise missiles.
It can track and engage up to 300 targets at the same time and has an altitude ceiling of 27 kilometers (17 miles).
AN AIR MISSILE SYSTEM BECOMES URGENT DUE TO SYRIA WAR
Western governments have expressed concern over the deal - which Erdoğan said in July had been signed - as it cannot be integrated into the NATO system.
Turkey said in April that NATO ally nations had not presented a "financially effective" offer on alternative missile defense systems.
Turkey's need for an air missile defense system once again became urgent with the start of the civil war in Syria, a country which has a sizeable ballistic missile stockpile able to strike a large portion of Turkey's territory, in addition to biological and chemical weapons.
Turkish officials are concerned that the missiles could be used by the Assad regime in case of a unilateral military conflict or an international military intervention, while the possibility of the missiles falling into the hands of a terrorist group poses greater danger.
The country had to rely on Patriot batteries provided by its NATO allies Germany, the Netherlands and Spain during the conflict.
Turkey faced similar worries during the Iran-Iraq War and the First and Second Gulf Wars due to the ballistic missiles possessed by those countries.
