Declarations by Russia and Turkey last week reviving plans for the Turkish Stream natural gas pipeline have worried EU diplomats who see it strengthening Moscow's hand.
EU officials fear that Turkish Stream will be expanded to bypass Ukraine as a transit route for supplies to Europe, increasing dependence on Russian gas export monopoly Gazprom and shutting in alternative supplies from the Caspian region.
"Turkey's new friendship with Russia might become an issue if Russia tries to replace Turkey for Ukraine. It makes sense for Turkey to get cheap gas from Russia, but it will come with strings attached: That is likely to be a problem for us," Reuters cited a senior EU official as saying.
EU officials will be watching warily as Erdogan and his Russian counterpart Vladimir Putin are set to agree a deal on Turkish Stream on August 9 at their first meeting since Russia imposed sanctions over Turkey's shooting down of the jet near the Syrian border last November.
