BRUSSELS, July 3 (RIA Novosti) -- An intergovernmental agreement on the Nabucco gas pipeline project will be signed on July 13 in Ankara, Turkey by 12 member states, a spokesman for the European Commission's energy policy said on Friday.

Ferran Tarradellas Espuny said the EC "has received an invitation to the signing ceremony" but declined to comment on the agreement, which has yet to be officially published.

He said the agreement was based on the principles "of mutual solidarity, mutual equality and interdependence."

The Nabucco project, estimated at $7.9 billion, is designed to pump Central Asian via Turkey to Austria through Bulgaria, Romania and Hungary.

Among the potential gas suppliers for the pipeline are Azerbaijan, Uzbekistan, Turkmenistan, Iran and Iraq.

The project will be a continuation of the existing Baku-Tbilisi-Erzurum pipeline and is to transport 20 billion cubic meters of gas a year. Two-thirds of the pipe length will pass across the Turkish territory.