Russian President Vladimir Putin has warned Ukraine not to reject a reduced gas price offer, but Kiev has rebuffed the proposal as key EU-mediated talks to resolve the dispute ended in deadlock.
Moscow and Kiev exchanged barbs after nearly five hours of haggling in Brussels failed to yield a deal on Wednesday.
"If our offer is rejected then we will shift to a whole other level," Putin told a government meeting in Moscow.
"That is not our choice and we do not want that."
The Russian strongman said Russia was offering Kiev a $US100 ($A108) "discount" for a final price of $US385 per 1000 cubic metres and accused Kiev of driving the negotiations into a "dead end" by demanding further reductions.
However, Ukraine Energy Minister Yuriy Prodan said after meeting with his Russian counterpart Alexander Novak, that Kiev could not accept an offer that could easily be withdrawn if Moscow changed its mind.
Ukraine wanted a price set by the market laid down in a commercial contract, Prodan said, but "unfortunately Russia proposed a way of fixing the price which I would call political".
However, EU Energy Commissioner Guenther Oettinger, who is brokering the negotiations, said that in his opinion the talks had established some common ground.
"We are still in negotiations," he said.
"I can see movement on both sides and both sides will need to continue to move."
The talks are being closely watched to see if both sides really want to bring some sort of closure to an unprecedented stand-off that began with pro-EU protests in Kiev in November.
If successful, they would build on a peace push by Kiev's new President Petro Poroshenko, who on Tuesday ordered the creation of humanitarian corridors in the country's conflict-torn separatist east, meeting a key Russian demand.
The latest round of talks began on a positive note after Russian gas giant Gazprom said early on Wednesday that it was delaying by five days a deadline for Ukraine to start paying for gas ahead of time, or risk a cut in its supply.
Moscow says Kiev owes it $US4.5 billion in outstanding bills, but Ukraine has refused to pay in protest at Russia's decision to nearly double the price in the wake of the February ouster of Kremlin-friendly president Viktor Yanukovych.
