The high-stakes meeting between Russian Energy Minister Alexander Novak, his Ukrainian counterpart Yuri Prodan and European Energy Commissioner Guenther Oettinger began as planned, a commission spokeswoman said.
“We had bilaterals with both sides and a trilateral meeting will start very soon,” spokeswoman Marlene Holzner said.
“It’s not possible to say when the talks will end,” she added.
Russia in mid-June cut supplies to Ukraine, demanding the new pro-Western government in Kiev pay steeply increased prices up front for any new deliveries after it ran up what Moscow says is an unpaid bill of $5.3 billion (4.1 billion euros).
That supply cut heightened concerns that Europe, which gets about a third of its gas from Russia of which about a half transits via Ukraine, could be badly affected by the dispute this winter.
But hopes for a deal improved after Ukrainian President Petro Poroshenko and Russiancounterpart Vladimir Putin reached a preliminary deal at an EU summit last week in Milan.