Escalating tensions between the West and Russia over Ukraine have raised concerns about vital Russian oil and gas flows to Europe, prompting the United States to offer reassurances that it will help its European allies find alternative supplies. But that task may be mission impossible for Washington.
Even without a build-up of Russian forces on Ukraine's border and US warnings of painful sanctions if tanks rumble across, the world's oil and gas producers have struggled to meet global demand, pushing crude prices to their highest since 2014 and driving European gas prices to stratospheric levels last year.
Russia denies it has plans to invade. But if a crisis does flare, there are few, if any, alternatives to fill a gap caused by any disruption to supplies from Russia, one of the world's top three oil producers and the second biggest gas producer.