President Erdogan says that he and his Russian counterpart will see the missile deal through; and first deposit has reportedly been paid.
Ankara has already paid a deposit to Moscow to buy Russian S-400 Triumf missile systems, Turkish President Recep Tayyip Erdogan told reporters on Monday.
The deal, which it is believed to cost between $2 billion and $3 billion, has bothered the US, which has expressed concern over the purchase.
"The S-400 missile system deal has already been signed by our friends. As far as I know, the first deposit was also transferred. This process will continue between Turkey and Russia. Both [Russian] President [Vladimir] Putin and I are determined to realise this deal," Erdogan said, speaking to reporters aboard the presidential plane on the way back from a conference in Astana.
A more definitive statement than Erdogan's comments that "as far as I know" could not be obtained by TRT World from Turkish defence ministry officials. They declined to confirm if any payment had been made, saying that they could not reveal details of the deal.
Russia's presidential aide Vladimir Kozhin confirmed the deal, telling the the state-run TASS news agency that "the contract has been signed" and "it is about to be executed."
Kozhin said: "There is a waiting list of likely buyers eager to have this system."
NATO allies Turkey and the US have been at odds over Washington's support and provision of military hardware to the YPG militia group in northern Syria. Turkey considers the YPG a terrorist organisation.
"For instance, we were unable to acquire drones from our allies. They were demanding an exorbitant sum. We were not demanding that they do it for free, mind you. They provide tanks, armoured vehicles, and armament to terrorist organisations, yet do not allow us to acquire certain defence equipment. So, we started to produce our own drones and armed drones," Erdogan said.
Turkey also criticises its allies for not selling weapons or sharing technology with them.
The S-400 deal includes the sharing of technology with Ankara.
"We make our own decisions regarding our independence and we are obliged to take the necessary measures in defence and security. If we're having issues in acquiring certain defence instruments and our attempts are met with obstacles, what we're going to do is simple: We will take care of ourselves."
The US has also criticised the deal because of the S-400's incompatibility with NATO systems.
"The problem is, how do you interoperate in the NATO system with Russians? They'll never interoperate," US Defense Secretary James Mattis has previously told reporters.
The S-400 is Russia's next-generation, most advanced long-range anti-aircraft missile system.
It is designed to detect, track and then destroy any machine that poses a threat.
It has a 400 km-range and can work with four different types of missiles with different starting weight and launch ranges.