Russia increased pressure on investors in its two Pacific energy projects which once helped Moscow rebuild its economy, blaming ExxonMobil for falling oil output at Sakhalin-1 and giving shareholders of Sakhalin-2 a month to claim their stakes. Western countries and allies, including Japan, piled sanctions on Russia after it sent troops into Ukraine in late February. Moscow retaliated by creating obstacles for Western businesses and their allies leaving Russia, and in some rare cases seized their assets. Sakhalin-1 and Sakhalin-2 offshore projects in Russia's far east were launched in 1990s when Moscow was wooing deep-pocketed foreign investors to bring cash it needed to rebuild its economy after the fall of the Soviet Union. On Thursday, Russian state energy champion Rosneft blamed a slump in oil production at Sakhalin-1 - and where it has a stake - on the operator, ExxonMobil.