UPDATE 1-Russia seals Central Asian gas pipeline deal

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MOSCOW, Dec 20 (Reuters) - Russia, Turkmenistan and Kazakhstan signed on Thursday a deal to build a pipeline that will allow Moscow to keep Central Asian gas flows to the West under its control for years to come.

The trilateral agreement was signed in Moscow in the presence of President Vladimir Putin of Russia and President Nursultan Nazarbayev of Kazakhstan.

"The creation of this new energy artery will ensure major long-term and stable gas supplies to our partners and will become another serious contribution of our countries to the strengthening of Europe's energy security," Putin told a news conference.

Russian Energy Minister Viktor Khristenko said the link, skirting the Caspian Sea, would be built by the end of 2010. It would export 20 billion cubic metres of gas a year -- enough to cover demand of a country such as France for almost half a year.

Turkmenistan and Kazakhstan control large reserves but do not have access to global markets other than via pipelines of Russia's export monopoly Gazprom (GAZP.MM), which is already buying 50 bcm of Turkmen and over 10 bcm of Kazakh gas a year.

The two countries have repeatedly said they would look to diversify their export routes.

This diversification could include building pipelines to China and under the Caspian Sea to join the Nabucco link - a cornerstone of Europe's strategy to diversify away from heavy dependence on the Russian energy.

Analysts have said Moscow masterminded the new Caspian pipeline to eliminate rival projects, including Nabucco, and maintain a quarter of Europe's gas market share.

Without the Turkmen and Kazakh gas, Nabucco can only rely on the Azeri gas output, which can reach Europe via the territories of Turkey and Bulgaria.

But Gazprom is trying to block the Azeri supplies for Nabucco as it has a rival project to supply southern Europe with Russian gas by building a pipeline to Bulgaria under the Black Sea. This project is being jointly developed with Italy's energy group ENI (ENI.MI). (Reporting by Oleg Shchedrov, writing by Dmitry Zhdannikov; editing by Douglas Busvine)