Bulgaria wants the European Commission to revive plans for the Nabucco pipeline that would bring gas from the Shah Deniz gas field in the Azeri territorial waters of the Caspian Sea.
Keen to diversify its energy supplies due to the Ukraine crisis, Bulgaria meets more than 80% of its gas needs with imports from Russia.
Sofia was caught off guard by President Vladimir Putin's surprise announcement in December that Russia was abandoning plans for the South Stream pipeline that would have supplied gas to Europe via Bulgaria, while bypassing Ukraine.
Both Nabucco and South Stream were designed to pass through Bulgarian territory. Nabucco was originally an American project to bring gas to Europe from sources other than Russia, an idea strongly resented by Moscow.
Keen to diversify its energy supplies due to the Ukraine crisis, Bulgaria meets more than 80% of its gas needs with imports from Russia.
Nabucco was backed by Western powers, but was shelved in part because there was not enough demand to sustain both it and South Stream. Bulgaria, which would have benefited from charging transit fees for South Stream, sees reviving Nabucco as a way to compensate for its loss.
Edited from various sources by Elizabeth Corner