LONDON—Natural gas exports from the U.S. are unlikely to help ease the tensions between Europe and Russia over Ukraine as the first such shipments are about two years away, a senior executive from oil and gas company BG Group PLC said Tuesday. The U.S. has vast supplies of cheap natural gas thanks to the fracking boom and could become one of the world’s top three exporters of liquefied natural gas by 2025, BG said. Over the past week, some U.S. politicians have urged the Obama administration to speed up oil and natural gas exports to weaken Russia’s hand over Ukraine. Russia supplies about 30% of Europe’s gas requirements, half of which transit via Ukraine, a factor some believe has stifled European opposition to Russia’s annexation of Crimea. Federal law places heavy restrictions on U.S. companies from exporting natural gas to countries, like those in Europe, that aren’t among its […]