Western capitals are increasingly alarmed about the deepening economic co-operation between Turkey’s president Recep Tayyip Erdo?an and Vladimir Putin, warning of the mounting risk that the Nato member state could be hit by punitive retaliation if it helps Russia avoid sanctions.Six western officials told the Financial Times that they were concerned about the pledge made on Friday by the Turkish and Russian leaders to expand their co-operation on trade and energy after a four-hour meeting in Sochi.

One EU official said that the 27-member bloc was monitoring Turkish-Russian co-operation “more and more closely”, voicing concern that Turkey was “increasingly” becoming a platform for trade with Russia.

Another described Turkey’s behaviour towards Russia as “very opportunistic”, adding: “We are trying to make the Turks pay attention to our concerns.”