Despite becoming the first country to sign up for the South Stream project amid the fanfare of then Russian president Vladimir Putin's visit to Sofia in January 2008, Bulgaria's commitment to the Russian-Italian project has shown cracks as of late.

After Gazprom has tried to amend the terms to have part of Bulgaria's existing gas network become part of the project, which authorities in Sofia oppose, it emerged that the two sides were yet to settle the size of the transit fees Bulgaria was due to receive.

"There are attempts to sidestep the Bulgarian interests. If Bulgaria wins nothing from transit, but has to spend heavily on investment and maintenance costs, then what is the point of the project," Economy Minister Petar Dimitrov said on April 24, on the sidelines of an energy summit in Sofia.

Without specifying the exact amount, Dimitrov said that Bulgaria wanted the transit fees to more than break even the costs within 15 years of the pipeline's launch.

Bulgarian Prime Minister Sergei Stanishev will travel to Moscow on April 27 to meet with Putin and it was possible that a deal would be signed then, Dimitrov said.

The issue is further complicated by the fact that Bulgaria wants Gazprom to amend its current deal with the country, eliminating intermediators along the supply chain and guaranteeing deliveries.

"A company registered in Bulgaria, such as Overgas Inc, cannot be responsible for halted deliveries. Nothing depends on it," Dimitrov said.

In January, with Russia and Ukraine locked in price dispute, Gazprom cut deliveries to Europe, with Bulgaria suffering the worst because about 90 per cent of its gas comes from a Russian pipeline that passes through Ukraine.

Gazprom refused pay any damages, which some estimates put at as high as 500 million leva, blaming Ukraine for the dispute.