Turkey will be a major player in the Nabucco project
European governments are due to sign an agreement on the Nabucco gas pipeline on 13 July, the European Commission has announced.
The Nabucco pipeline will bring Central Asian gas to western Europe via Turkey and the Balkans, bypassing Russia.
Turkey, Bulgaria, Romania, Hungary and Austria - the pipeline's five transit countries - will sign the accord.
The pipeline - which will compete with new rival Russian pipelines - should be operational by 2014.
Germany is also a member of the consortium, but the pipeline will not cross Germany.
"I can confirm that the Commission has received an invitation to the signing ceremony of the intergovernmental agreement on the Nabucco pipeline on July 13 in Ankara," a European Commission spokesman told a news briefing.
Plans for the Nabucco pipeline come as European Union states are keen to reduce their reliance upon Russian gas because of Russia's numerous price disputes in recent years with Ukraine.
These rows have seen Gazprom temporarily cut supplies to Ukraine, which in turn has reduced Russian gas deliveries to western Europe that are piped through Russia's neighbour.
Work is under way on Russian pipelines which will bypass Ukraine. Like Nabucco, the Russian South Stream pipeline will transit the Balkans.
The major sources of gas for Nabucco are expected to be Azerbaijan, Kazakhstan and Turkmenistan.
Azerbaijan has already promised Gazprom, the Russian state gas company, priority when it comes to buying gas.