MOSCOW (Reuters) - Russia signalled on Wednesday that it could toughen demands for gas payments from Ukraine if Kiev fails to fulfil existing agreements, adding to pressure on an ex-Soviet neighbour gripped by an economic and political crisis.
Moscow is concerned about Ukraine's growing debt for gas but will not review deals as long as Kiev meets its obligations, Russian President Vladimir Putin's spokesman, Dmitry Peskov, said on Kommersant-FM radio.
"Of course we are concerned by the growing debt for gas supplies ... but we hope that our Ukrainian partners will stick to all the clauses of the current agreement," Peskov said.
Ukrainian energy firm Naftogas said this week that non-payments by its clients mean it may fail to pay Russian gas export monopoly Gazprom on time for imports, a bill the Kremlin-controlled company says has risen to $3.3 billion.
"There are contracts ... that clearly state the price of gas supplies, how it is paid and when," Peskov said. "And so if the case of elementary fulfilment of the existing document, there is no reason and will be no reason to review anything."
He gave no details. A clause in a 2009 gas contract allows for Gazprom to seek pre-payment for gas supplies, and if invoked could increase the risk of a Ukrainian default.
(Reporting by Vladimir Soldatkin; Editing by Steve Gutterman/Mark Heinrich)