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MOSCOW — Russian President Vladimir Putin turned up the heat on Ukraine on Wednesday by threatening to demand advance payment for gas supplies, a move designed to exert economic pressure as Ukraine confronts possible bankruptcy, a mutiny by pro-Russian separatists in the east, and a Russian military buildup across the border.
NATO’s top commander in Europe warned that the alliance could respond to the Russian military threat against Ukraine by deploying U.S. troops to Eastern Europe, but Putin’s latest tactics suggest he may be aiming to secure Russia’s clout with its neighbor without invading.
Speaking at a Cabinet session, the Russian leader voiced hope that diplomatic efforts to ease the Ukrainian crisis would yield ‘‘positive results,’’ an apparent reference to talks set for next week that will bring together the U.S., the European Union, Russia, and Ukraine for the first time.