"We know these Russian games: a discount is set by a Russian government decision and rescinded by a Russian government decision. Our position remains the same - we want a change to the contract," Prime Minister Arseniy Yatsenyuk said.
"All the traps and hooks that Russia is once again laying out for us are unacceptable," he told a government meeting.
Yatsenyuk's comments came moments before the two sides were due to launch a new round of EU-mediated talks in Brussels aimed at averting a Russian gas cut over unpaid bills.
Ukraine has amassed debts of some USD 4.5 billion, according to Moscow, but is refusing to pay the bill until Russia reduces the price set in a disputed contract the two sides signed in 2009.
Moscow last year awarded a price rebate for Kiev for its decision to reject a major EU trade pact, lowering the price to USD 268.50 from USD 485.50 for 1,000 cubic metres of gas.
Russia's state natural gas giant Gazprom today pushed back the gas cut deadline until June 16 to give the two sides more time to reach a deal.
