AFP/Berlin

The chief European Union energy official warned Russia on Tuesday not to use gas supplies as a weapon in its standoff with Ukraine over the fate of its neighbour's separatist east.

EU Energy Commissioner Guenther Oettinger said he hoped to reach an "interim solution" with Russia over its gas supply cut to Ukraine when the three sides meet for crunch talks in Berlin on Friday.

Russia halted all gas sales to the ex-Soviet nation in June after Ukraine balked at paying a higher price imposed by Moscow in the wake of the February ouster in Kiev of a pro-Kremlin president.

Ukraine still transports volumes intended for Russia's other European clients. But EU nations fear that Kiev may be forced to tap into those flows once the winter heating season begins.

"The gas sector and the energy sector as a whole should not be a political tool," Oettinger told a forum in Kiev devoted to European energy security.

"It should not be a weapon in these difficult times, in the crisis between Ukraine and Russia and between Europe and Russia."

Energy giant Russia supplies Europe with about a third of its gas needs through a handful of Soviet-era pipelines and the new Nord Stream link that runs under the Baltic Sea and connects directly with Germany.

Ukraine currently transports half of the Russian gas used in European nations.

But countries such as Italy receive all their Russia supplies through the Ukrainian link.

Russia is also currently constructing a South Stream link that would also avoid Ukraine and supply southern European client states.

Oettinger said he hoped to reach a temporary solution to Russia's gas dispute with Ukraine when the sides meet in Germany.

"We want to avoid the worst case scenario," said Oettinger.

"We are checking again to come to a pragmatic solution, an interim solution, a compromise with our Russian contracting partners."

But he hinted that EU nations may be forced to expand its current list of sanctions against Russia to include its gas sector if not quick fix is found.

"It was our and my position to avoid sanctions into... any gas industries," he said.

"It is our clear preference to come to an interim solution and to get enough gas from Russia."

The European Union banned the sale of advanced equipment to Russia's oil companies last month.

But it stopped short of following the US lead and taking the same step against Russia's state-held gas giant Gazprom.