Bulgaria said on Wednesday it was pulling out of a long-stalled pipeline project meant to bring Russian oil to Greece through its territory, but Athens and Moscow said they remained committed.

"Bulgaria suggests cancelling the project by mutual agreement. Otherwise, it will back out unilaterally in 12 months," Finance Minister Simeon Djankov said.

The government said the project, originally estimated in 2007 to cost $900 million (710 million euros at the time), was no longer seen as being economically viable.

Despite pressure from its partners, Bulgaria has also repeatedly expressed reservations about the environmental impact of the 280-kilometre (175-mile) pipeline because it would pass through nature reserves.

It would have allowed Russia to transport oil to Europe while bypassing the busy Bosphorus strait, running overland from the Bulgarian Black Sea port of Burgas to Alexandroupolis on the Aegean Sea in Greece.

Djankov said Sofia would pay the 12 million leva (6.1 million euros, $8.2 million) it owes to the company founded to construct the pipeline, 51-percent owned by Russia's oil pipeline monopoly Transneft, along with Rosneft and Gazprom Neft, and 24.5 percent each by Bulgaria and Greece.

Both crisis-hit Greece and Moscow said Wednesday they were sticking with the project.

"We do not have any official information ... on a Bulgarian withdrawal," said Yannis Maniatis, Greece's deputy energy minister.

"Greece remains attached to its strategic choice, in view of the usefulness of the pipeline for both Greece and Bulgaria as well as for supporting Europe's energy security."

He said that Greece was working to address the environmental issues around the project.

A spokesman of Russia's Transneft, Igor Diomin, told Bulgaria's national radio on Wednesday that he hoped the "project will be frozen but not buried."

"We still continue to believe that the project is of interest to all its participants: Bulgaria, Greece, Russia and also the US," he said.

A meeting of the shareholders in the project company, Trans-Balkan Pipeline, next Wednesday in Amsterdam would decide on the future of the project, Diomin said.

Bulgaria's right-wing government has recently expressed reservations on the cost effectiveness of another project with Russia to build a 2,000-megawatt nuclear power plant near Belene on the Danube, threatening to drop it altogether.

The government however granted last week status of national importance to work on its stretch of the 3,600-kilometre (2,200-mile) South Stream gas pipeline to carry Russian gas to Europe.

Sofia also plans to build a 100-kilometre (60-mile) pipeline to link up its gas network to the Greek one that will enable it to receive gas from the Caspian region via the ITGI pipeline project linking Turkey to Greece and Italy.