Turkey and Russia have agreed to bring forward to July 2019 the delivery of S-400 air defence missile systems to Ankara, a Turkish official said, in a purchase that has raised eyebrows among NATO allies, AFP reports.

“We brought forward the delivery date in the contract signed with Russia for the acquisition of S-400 systems and got an earlier date of July 2019,” Ismail Demir, Turkish Defence Industries undersecretary, wrote on Twitter late on Tuesday.

His announcement came after Russian President Vladimir Putin held several hours of meeting with Turkish counterpart Recep Tayyip Erdogan in Ankara.

At the press conference, Putin said he and Erdogan had decided to “speed up” the delivery of the S-400 air defence missile systems to Ankara, without providing a precise date.

Russian officials had said in December that the first deliveries in the $2 billion deal were likely to begin at the end of 2019 or beginning of 2020.

Putin and Erdogan have forged an increasingly close alliance in recent months, from burgeoning energy ties to holding talks to end the Syria crisis.

In a sign of the importance of the partnership, Putin’s visit to Turkey is his first trip abroad since he won a historic fourth presidential mandate in March 18 polls.

Erdogan said Tuesday that Turkey was in no mood to listen to criticism from the West over the purchase of the S-400 systems, saying “this issue is now closed”.

According to Russian press reports, Turkey has been interested in a technology transfer and even joint production of the S-400 with Russia, a prospect that has been resisted by some in the Moscow security services.

Putin refused to discuss the issue saying “these are exclusively commercial questions” rather than political ones.