The scheduled delivery of Russian S-400 surface-to-air missile batteries to Turkey has been brought forward to July 2019 from the first quarter of 2020, the Turkish undersecretary for defence industries Ismail Demir said on April 4.

During the first day of his two-day visit to Turkey on April 3, Russian President Vladimir Putin announced that a contract to supply the S-400 defence hardware to Turkey was a priority in military cooperation between Moscow and Ankara and would be speeded up.

Subsequently Demir said on Twitter: "We brought forward the delivery date in the accord signed with Russia to provide the S-400 system and got a date of July 2019."

The news that the $2.5bn deal has been accelerated will do nothing to ease anxieties among Turkey’s fellow Nato members over Ankara’s growing closeness to the Kremlin. What’s more, aside from reiterating Turkey’s commitment to acquiring the S-400 anti-aircraft system—which cannot be integrated into Nato’s military architecture—at a news conference during the Putin visit Turkish President Recep Tayyip Erdogan said that Turkey may cooperate with Russia on defence projects besides the S-400 missile system, though he did not give any further details. There have been some signs that the US may try to block the S-400 deal, perhaps by refusing delivery of F-35 warplanes to Turkey if it goes ahead or by threatening sanctions.

Turkey’s relations with Russia all but collapsed in 2015 when the Turks shot down a Russian fighter-bomber near the Syrian border, but there has been a strong rapprochement since then. That was underlined by Turkey remaining one of the few Nato partners that did not expel Russian diplomats in response to the nerve agent attack against the Skripals in the UK in March.