* EU Commission must decide on gas pipeline's legality
* Russia says Nord Stream is the practical, economic answer
* Eastern Europe, Baltics nervous about Russia dependency
BRUSSELS, Dec 17 (Reuters) - EU leaders are set to agree on Friday that the Nord Stream pipeline extension to double shipments of Russian gas directly to Germany must abide by EU anti-monopoly and security of energy supply rules, EU diplomats said.
Russia's Gazprom, together with a group of European shareholders, in September signed an agreement to develop Nord Stream-2, prompting stiff opposition from a group of EU nations that say the project further destabilises Ukraine and divides the European Union.
A draft document for the EU summit, seen by Reuters, says any new infrastructure must "entirely comply" with all EU goals to diversify energy suppliers, sources and routes and cut dependency on Russian gas.
"The words 'new infrastructure' refer to Nord Stream-2, though they don't say so out loud," one diplomat said on condition of anonymity.
The diplomat expected the wording on pipeline infrastructure to be adopted in the final version of the document, although it would then be up to the European Commission, the EU executive, to act.
So far the Commission has said it is in touch with the German regulator and that it is in the process of deciding on the legality of the Nord Stream-2 project.
Alexander Rahr, a Russia expert at a German-Russian forum in Berlin who advises Gazprom, said Nord Stream-2 was the most pragmatic solution to shoring up Europe's energy security.
Over the next 15-20 years, he said Europe's own production would fall and a shift away from coal, the most polluting fossil fuel, would drive demand for gas.
Referring to opposition to Nord Stream, particularly from Poland and the Baltic States, which have begun importing liquefied natural gas (LNG) to curb their dependence on Russian gas, Rahr said pipeline shipment was cheaper over the long term.
"The Poles and the Balkan states have found ways to receive LNG," he said. "Let some time pass and see if the diversification is real. They will come to a point when they start to count their money." (Reporting by Barbara Lewis and Alissa de Carbonnel; Editing by Dale Hudson)