Bulgarian Prime Minister Plamen Oresharski has announced that Bulgaria is suspending work on the disputed Russian-backed South Stream gas pipeline following criticism from the European Union and United States.
Oresharski, speaking after a meeting with U.S. senators, said, "I have ordered all work to be stopped. We will decide on further developments following consultations with Brussels."
Russia's Energy Ministry said that Moscow has not yet received any official notifications from Bulgaria about the suspension.
South Stream is a 2,380-kilometer pipeline planned to transport Russian natural gas to the EU bypassing Ukraine.
Gas disputes have marred relations between Moscow and Kyiv, including during the current crisis in Ukraine.
Gas was to be pumped from 2015 to the Bulgaria’s Black Sea port of Varna before extending overland through Serbia, Hungary, and Slovenia to supply gas to Western Europe via Italy and Austria.
The EU has warned Moscow that the pipeline breaks the bloc's rules, notably when it comes to a planned monopoly of Russia's Gazprom over it.
The European Commission, the 28-nation bloc's executive, has also stepped up pressure on member Bulgaria, laying the groundwork for an EU infringement procedure that could eventually result in hefty fines for Sofia.
The commission is concerned that the contracts for the Bulgarian portion of South Stream were not awarded transparently.
Bulgaria, which joined the EU in 2007, is nearly totally dependent on Russian gas.
The South Stream dispute is likely to be discussed on June 9, when officials from Ukraine, Russia, and the EU hold talks in Brussels in an effort to resolve Kyiv's natural-gas debt to Moscow.
A Russian Energy Ministry official said the three sides will also negotiate a price for Ukraine's gas imports from Russia.
Russian gas giant Gazprom nearly doubled the price of natural gas for Ukraine after the February ouster of President Viktor Yanukovych, a Moscow ally.
Ukraine has insisted on paying $268.5 per 1,000 cubic meters for Russian natural gas, while Moscow has said the price was increased to $485 per 1,000 cubic meters.
Ukrainian Prime Minister Arseniy Yatsenyuk has threatened to take the issue to an international arbitration court in Stockholm if Moscow does not agree to the lower price.
But he said there could be a compromise on the price.
Based on reporting by Reuters, AFP, and ITAR-TASS