Russian President Vladimir Putin told European leaders that Ukraine’s growing gas debts to Moscow can threaten supplies to Europe, according to his press secretary.

Dmitry Peskov told state news agency RIA Novosti Thursday that Mr. Putin “expressed his utmost concern” to European leaders about the growing gas debts of Ukraine, which Moscow says owes Russia over $16 billion. Mr. Peskov did not otherwise discuss Mr. Putin’s message, but said it contained “urgent measures, as the situation requires no delay.”

The move is designed to exert economic pressure on Europe, which receive a large portion of its gas from Russia through Ukraine. Mr. Putin has tightened the economic screws on the cash-strapped Kiev government since it came to power in February, when its Russia-leaning president fled the country after months of protest.

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