KIEV, March 31 – Russia again has showed that its key interest is to prevent any changes in the Ukrainian gas transportation system, James Sherr, head of the Russia and Eurasia Program at the Royal Institute of International Affairs, said in an interview with the Dzerkalo Tyzhnya newspaper.

He was commenting on a statement by Russian Prime Minister Vladimir Putin on the agreement between Ukraine and the European Union on the upgrade of the Ukrainian gas transportation system, which said in particular, that if Russia's interests are ignored, Russia should revise its principles in its relations with its partners.