The United States and European Union are poised to stop billions of dollars in oil exploration in Russia by the world's largest energy companies, including Exxon Mobil Corp and BP Plc, according to a report on Wednesday. The new sanctions would prevent U.S. and European cooperation in searching Russia's Arctic, deep seas or shale formations for crude, Bloomberg reported, citing three U.S. officials who spoke on condition of anonymity because the measures have not been made public.