While Ukraine and Russia are locked in a bitter dispute over energy payments, EU states are apprehensive the conflict could lead to energy shortages in the bloc.
The standoff between Ukraine and Russia over gas prices hit a new low Monday, exacerbating fears that a halt in natural gas shipments to Kyiv could ultimately threaten Europe's own energy supplies.
Hours after Moscow halted deliveries to Ukraine on Monday, the head of Russia's Gazprom said Kyiv could illegally divert gas destined for the EU should the country run into shortages.
Half of the gas the EU imports from Russia is transported through pipelines in the Ukraine.
Kyiv has promised to not renege on its gas transport commitments and has said it has enough gas in underground storage to meet its own needs until December.
Speaking after the latest round of negotiations ended without a deal, Guenther Oettinger, the European energy commissioner, said the EU would be wise to top off its gas storage.
"If the store is not filled then perhaps we all will have a problem in winter," Oettinger said.
The German politician's remarks underscored a wider unease in the EU about potential energy shortages, especially in Germany, which relies on Russia for the lion's share of its natural gas imports.
In total, Germany burned through 1.179 million terajoules worth of natural gas in the first three months of 2014 - 31.6 percent of which came from Russia. Germany imported around four-fifths of the natural gas it consumed, and of those imports, 38 percent came from Russia.
As far as exporters of natural gas to Germany went, Norway was in a distant second with 291,000 terajoules from January to March this year, or 26 percent of the natural gas Germany imported. In third place the Netherlands with 20 percent.
Less in total, but more from Russia
Compared to a year ago, Germany consumed 17.7 percent less natural gas, but at the same time the amount of gas it imported from Russia rose by 11.7 percent.
For its part, the German government has said it sees no risk of energy shortages.
"We perceive no threat to the security of our supply in Germany," a spokesman from the economics ministry said Monday.
While roughly half of the gas EU countries, including Germany, order from Russia is pumped through pipelines in Ukraine, the other half is transported via Belarus or through the North Stream pipeline in the Baltic Sea.
Were bottlenecks in supply to occur in Ukraine, the German ministry spokesman said, they could be overcome by rerouting gas through the North Stream pipeline, as it is only at two-thirds capacity currently.