Both Bulgaria and Russia have expressed their devotion to the South Stream project, but it is still early to judge which state would prove the winner, Valery Nesterov, an analyst at Russian investment company Troika Dialog, told local daily Vedomosti.

The two countries will now have to move ahead with complex negotiations concerning the price on gas transit, Nesterov said, commenting on the agreement sealed between the parties on the gas project.

According to the daily, South Stream could emerge as Russian gas giant Gazprom's most expensive project, whose price, however, has never been unveiled so far.

In February 2009, Gazprom said that the 3,000-kilometre route could be worth over EUR 24 billion. Later, the company's CEO Alexei Miller stated that capital expenditures on the project would amount to EUR 8.6 billion.

Nezavisimaya Gazeta, another Russian newspaper, wrote that the creation of the joint venture, which will be in charge of the Bulgarian section of the project, still does not mean a green light to the start of the construction.

"Making an investment decision will be a clear signal, but prospects at this stage are currently extremely difficult to predict," Exploration and Production magazine's analyst, Mikhail Krutikhin, noted.

The fact that many of the countries participating in the project were recently on the brink of default and may find difficulties in securing the necessary investments brings more uncertainty to the project, Krutikhin added