Potential investors are to be made familiar with four options drafted by Bulgaria as it aims to launch a "gas hub" project, gas grid operator Bulgartransgaz has said.

All possible versions of the hub, which the government has dubbed Balkan, will be showcased on September 5-6 at a conference organized by the state-owned company, news website Mediapool quotes its head, Georgi Gegov, as saying.

Under Sofia's current plans, the project will be run by a company with the state as a majority shareholder. Other shares will be distributed among potential investors. The venture will only operate the infrastructure built for the hub's purposes.

As many as 35 companies, many of them dealing with gas trade and transit, have confirmed attendance, according to Gegov. Other participants include the European Investment Bank, the European Bank for Reconstruction and Development, and pension and investment funds.

As of Tuesday morning, representatives of Russian energy giant Gazprom have not said whether they will be attending.

Bulgaria's Prime Minister Boyko Borisov announced his country intended on setting up the Balkan Gas Hub after Russian President Vladimir Putin announced his country would not build South Stream, a pipeline that was to carry gas to Central Europe via Bulgaria.

However, Borisov later argued Russia was one of the sources of gas needed for the Balkan gas hub project to be feasible.

Reportedly, he discussed the prospects to restart South Stream in a phone conversation with Putin earlier this month. The latter made clear his country would demand iron-clad guarantees that the project would be carried though.

Sofia is also pinning hopes on gas deliveries via Interconnector Greece-Bulgaria (IGB) that, once built, will be supplied by the Trans-Adriatic Pipeline (TAP) and, possibly, liquefied natural gas delivered to Greek and Turkish ports. The Eastring pipeline, proposed by Slovakia, is seen as another option.

Russia has been reluctant to comment on the project despite numerous demands from Bulgarian authorities, with Energy Minister Alexander Novak questioning earlier this year the gas sources it would use.