Russia will begin implementing the deal on deliveries of its advanced S-400 missile defense system to Turkey in 2019, Russia's state arms exporter Rosoboronexport said Tuesday.

"The contract is being implemented on the dates previously agreed. In 2019, we will begin to implement the contract," head of Rosoboronexport Alexandr Mikheyev said.

Rosoboronexport also said it would switch to using local currencies in deals with foreign trade partners, instead of using the U.S. dollar, as both Turkey and Russia are hit by sanctions imposed by Washington.

In September, Turkey agreed to buy two S-400s in a deal worth over $2 billion. Officials from Ankara have repeatedly said that the purchase of the S-400 systems was prompted to fulfill the country's security needs.

As a NATO member country, Turkey's decision to buy the Russian S-400 systems has raised concern among other NATO member countries. However, NATO Secretary-General Jens Stoltenberg ended speculations, saying member states have the sovereign right to make decisions regarding their military purchases.

The S-400 missile defense system 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.

The system can track and engage up to 300 targets at a time and has an altitude ceiling of 27 kilometers (17 miles). With the purchase of the S-400s, Ankara aims to build Turkey's first long-range air and anti-missile defense system to guard against threats in the region.

Moreover, Turkey seeks to build its own missile defense systems as the deal also involves the transfer of technology and know-how. The S-400 system, which was introduced in 2007, is the new generation of Russian missile systems, and so far Russia has only sold them to China and India.