Moscow said the European Union should halt talks on a proposed Caspian Sea pipeline to carry natural gas to Europe, characterising the bloc's involvement in the project that would by-pass Russia as "meddling" that could add to tensions in the region.
The 27-member bloc agreed on Monday to kick off negotiations to secure a pipeline deal with Turkmenistan and Azerbaijan - two of the five states bordering the Caspian Sea -- to allow gas from the region, which has the world's fourth-largest reserves, to flow directly to Europe.
An agreement would boost the EU-backed Nabucco pipeline project -- to build a pipeline between Turkey and Austria -- aimed at reducing the bloc's dependence on Russia for a quarter of its natural gas supplies. Russian gas deliveries to Europe have been interrupted as a result of chronic disputes with transit state Ukraine.
"Outside attempts to meddle in affairs in the Caspian... could very seriously complicate the situation in this region (and) negatively affect the ongoing five-party negotiations on the Caspian Sea's legal status," the Russian Foreign Ministry said on its website.
The ministry statement called on the European Union's executive "to respect the position of Russia and the other member state of the Caspian Five and refrain from action."
Russia and the other Caspian Sea littoral states -- Iran, Kazakhstan, Azerbaijan and Turkmenistan -- have been locked in sensitive talks over dividing claims to the sea's huge hydrocarbon reserves currently regulated by Soviet-era agreements.
Nabucco is among several pipelines schemes, including Russia's South Stream project, competing to build a trans-Caspian link with Azerbaijan and Turkmenistan.
Russia has long-term agreements to buy gas from Azerbaijan and Turkmenistan, former Soviet Union republics, which it views as part of its traditional sphere of influence.
Analysts say the Caspian Sea states only produce enough gas to fuel one of the costly new trans-Caspian pipeline projects.