Russian S-400 system
© Sputnik / Vitaliy Ankov
The US will 'sooner or later' have to face reality and understand that Turkey's purchase of Russian S-400 systems is a done deal, President Erdogan said, noting that the current agreement is just the beginning.

"We're done with the S-400. There is absolutely no question of stepping back on the S-400. It is a defense system, not an attack system," Turkish President Recep Tayyip Erdogan said on Saturday during a televised question and answer session with university students in Istanbul, adding that the first deliveries of the Russian anti-aircraft weapon system are expected in July.

Explaining that Russian military hardware is offered on "very favorable terms" and with no strings attached, Erdogan said that Ankara is also potentially seeking to acquire the next generation S-500 systems - or even engage in co-production partnership - once Russia completes development of its newest mobile surface-to-air missile system.

The $2.5 billion defense deal with Moscow enraged Washington, which threatened its NATO ally with all kinds of sanctions while offering to substitute the Russian systems with Patriot batteries - a carrot Ankara has been reluctant to accept. At the same time, Washington threatened to block the delivery of 100 F-35 jets purchased by Turkey, and terminate its participation in the F-35 program. Ankara, having invested $1.25 billion in the trillion-dollar program, is a vital partner, producing parts of fuselage, landing gear, and cockpit displays for the jets.

Ankara has repeatedly slammed Washington's coercive diplomacy, saying that Turkey is not a "slave" dancing to the US' tune when it comes to protecting the nation's sovereignty. Nevertheless, Erdogan said he has no doubts that the stealth jets will be delivered.

"They [the US] are passing the ball around in the midfield now, showing some reluctance," the president said. "But sooner or later, we will receive the F-35s. Not delivering them is not an option."