European Energy Commissioner Guenther Oettinger said Monday that Ukraine and Russia have made further progress in a dispute over gas prices and his proposal that Ukraine pay $2 billion of back debt by Thursday could pave the way for further talks Friday.

Speaking after three-way talks with Russia's and Ukraine's energy ministers, Oettinger said the two governments will study his proposal that Ukraine pay Russia $2 billion by Thursday and a further $500 million by June 7.

Oettinger, acting as a mediator in the capital of his home country, Germany, said if the governments agree to the deal, further talks about the gas price from April can be held from Friday. "We've achieved progress but we didn't achieve a breakthrough," he told reporters at a news conference in Berlin. "I believe an agreement is possible."