Russia will speed up the delivery of its S-400 air defense systems to Turkey at the latter’s request, said Russian presidential aide Vladimir Kozhin.

Talking to TV channel Rossiya 24, Kozhin, aide on military and technical cooperation to the president of Russia, said that Russia plans to start shipping the systems in early 2020.

“The contract is signed and it is being fulfilled. The Turkish side kept expressing its desire to speed it up and we have found an optimal option here: we met them halfway about speeding up the contract,” Kozhin said in an interview earlier this week.

Earlier, Sergey Chemezov, Head of Russia’s Rostec corporation, said that Turkey is buying four divisions of S-400s at a cost of $2.5 billion.

In November 2017, it was reported, citing Turkish Defense Minister Nurettin Canikli, that Russia would ship the first unit at the end of 2019.

Chemezov also said that Russia will issue credit to Ankara covering more than half the cost of the contract.

On March 10, Turkish Foreign Minister Mevlut Cavusoglu said that Turkey needs the air defense systems urgently because the country presently has none.

Last week, head of US European Command and Supreme Allied Commander Europe Curtis Scaparrotti said that the United States hoped that Turkey would change its decision on buying the Russian S-400 systems and warned that Ankara might face consequences over the move.

The deal has become a major concern for NATO. Earlier this month, NATO Deputy Secretary-General Rose Gottemoeller said that the S-400 does not integrate with NATO members’ systems, while NATO’s Military Committee Chairman Petr Pavel warned that although member nations have sovereignty in decision-making, they are also “sovereign in facing the consequences of that decision”.