Moscow : Russia Tuesday threatened to introduce advance payment for its future natural gas supply to Ukraine unless Kiev repays its debt.
"If our partners don't want to pay, we'll switch to pre-payment," reported Xinhua citing Russian Prime Minister Dmitry Medvedev during a phone conference on gas industry.
"If our partners don't fulfil their obligations, this affects situation in (Russian gas giant) Gazprom in general. Our contractors, I mean Ukraine, must understand that," he said.
On Tuesday, Kremlin spokesperson Dmitry Peskov said that Gazprom "has boundaries of its flexibility" in terms of debt repayment. "Now the time has come when this must be done," he told the Russia-24 TV channel.
Moscow and Kiev have been in a state of a permanent "gas war" since 2005. Under a contract between Ukraine's state-run Naftogaz and Gazprom, Kiev must pay for its gas imports no later than Oct 7 every year.
Ukrainian Prime Minister Mykola Azarov said Tuesday that his government is aware of problems with gas payments to Russia, but the problems "can hardly be called critical".
Azarov said, Naftogaz and Gazprom are the responsible business entities which should settle the issue.
Ukraine, which is paying nearly $410 per 1,000 cubic meters for Russian gas, has long been seeking to reduce gas purchases from its neighbour.