MOSCOW (Reuters) -- Russia sees a pledge by the European Union to help modernize Ukraine's gas infrastructure as "an unfriendly act" against Moscow, the Russian Foreign Ministry has said.
Brussels signed a cooperation agreement with Ukraine on modernizing the system this week, but Russia, which exports most of its gas through Ukraine's pipelines, was angry at being excluded from the talks.
The spat over Ukraine's pipeline system has revived fears of a repeat of a January gas dispute between Russia and Ukraine, when major EU customers were left without gas for nearly two weeks in the dead of winter.
"What happened in Brussels...at the forum was an unfriendly act in relation to Russia by both the European Union and Ukraine," Foreign Ministry spokesman Andrei Nesterenko told a news conference.
Russia's gas giant Gazprom supplies Europe with more than one-quarter of its gas, and around 80 percent of that goes via pipelines that cross Ukraine.
Russia's Prime Minister Vladimir Putin has threatened to review ties with the EU if Moscow's interests are ignored.