BRUSSELS — The United States on Wednesday called on Europe to wean itself from a dangerous dependency on Russian gas, saying it was time to stand together and bring an end to the Kremlin’s use of energy supplies as political leverage.

Left unsaid was the European Union’s reluctance to follow the United States headlong into shale gas extraction, which has transformed the global energy scene and turned the U.S. from importer into a nascent exporter. Or its refusal to fully re-embrace nuclear power in the wake of the Fukushima disaster in Japan.

And even if it tried to become independent, it would take Europe years to develop promising sources, such as shale deposits in Ukraine and Poland – and with no guarantees of success.

Europe’s reliance on Russia for a third of its energy needs has left the Kremlin in a position of power, emboldening it as it swept in to annex the Crimean Peninsula from Ukraine last month, with little more than diplomatic protest and a few sanctions in return.

Russia’s energy dominance was most recently highlighted when state-controlled Gazprom carried out its threat this week to raise natural gas rates for Ukraine. But Russia has turned off the valves to Europe before, in 2006 and 2009.

Despite its contentious history of dependence, European production has been in steady decline as aging nuclear plants go unreplaced, polluting coal declines in popularity and North Sea oil dwindles.

Secretary of State John Kerry’s call made clear that the United States wants Europe to take more responsibility for its own energy supply, rather than trusting what is increasingly seen as a politically fragile network of pipes all leading to Russia – with many of them passing through Ukraine.