"We have an intergovernmental agreement with Bulgaria," Shmatko told journalists on the sidelines of the International Economic Forum in St. Petersburg. "It stipulates certain information exchange procedures. We have not received any official notification."

"Nevertheless, we know that the Burgas-Alexandroupolis project is not progressing unlike the Belene Nuclear Power Plant project," he added, referring to another joint project.

Bulgaria's Prime Minister Boiko Borisov said last week the country would not go ahead with the pipeline or nuclear power plant projects, citing a lack of investment for the nuclear power plant and environmental concerns over the pipeline. Bulgaria's energy minister said that Sofia had yet to make the final decision on the two energy projects.

Borisov said he was misunderstood by media and an assessment on the environmental impact of the Burgas-Alexandroupolis pipeline would decide whether the project goes ahead.

"I would rather divide these two projects; they belong to [two] totally different weight categories. We know about the discussion on Burgas [oil pipeline] by the Bulgarian government," the Russian energy minister said. "But we have adopted a formal approach and expect an official notification from our colleagues."

Shmatko shrugged off concerns over Bulgaria's possible withdrawal from the Belene project.

"We believe there are no grounds for concerns that Bulgaria could abandon this project, and nobody has spoken about this," he said. "They are looking for a strategic European investor. In principle, we don't object to this. The only issue that worries us is time."