Russian energy giant Gazprom will be compelled to switch over to pre-paid gas deliveries to Ukraine or completely cut off natural gas supplies, should the country further violate its terms of payment, Putin wrote.

If Ukraine does not settle its 1.6 billion euro ($2.2 billion) energy bill, natural gas giant Gazprom would be "compelled to switch over to advance payment for gas deliveries, and in the event of further violation of the conditions of payment, will completely or partially cease gas deliveries," Putin wrote in the letter, acknowledging that this would be an extreme measure.

Talk of a gas cutoff came as Ukraine again defaulted on its gas debt in March, swelling past the November record of $1.45 billion.

“I would like to draw your attention to the fact that in March there was still a discount price applied, that is [the price was] $268.50 per 1,000 cubic meters of gas. And even at that price, Ukraine did not pay a single dollar,” the president said.

Putin also pointed to a whole string of discounts that Ukraine had been granted over the years, slashing Ukraine’s gas bill by almost a third. But the country failed to meet its contract obligations, prompting Gazprom to rethink its delivery strategy, the Russian leader said.

“We fully realize that this [move] increases the risk of natural gas passing through Ukraine’s territory being siphoned off as it heads to European consumers. We also realize that this may make it difficult for Ukraine to accumulate sufficient gas reserves for use in the autumn and winter period,” Putin wrote.

Appeal to share the burden

"Russia cannot and should not unilaterally bear the burden of supporting Ukraine’s economy by providing discounts and forgiving debts and, as point of fact, using these subsidies to cover Ukraine’s deficit in its trade with EU member states,” said Putin.

Putin called on the country’s EU partners to join consultations at the ministerial level to help Ukraine’s economy out of the woods.

"It goes without saying that Russia is prepared to participate in the effort to stabilize and restore Ukraine's economy. However, not in a unilateral way, but on equal conditions with our European partners," Putin wrote.

"It is also essential to take into account the actual investments, contributions and expenditures that Russia has shouldered by itself alone for such a long time in supporting Ukraine. As we see it, only such an approach would be fair and balanced, and only such an approach can lead to success," Putin said.

"The fact that our European partners have unilaterally withdrawn from the concerted efforts to resolve the Ukrainian crisis, and even from holding consultations with the Russian side, leaves Russia no alternative," he said.

The missive, whose contents were released by the Kremlin, was sent to the heads of 18 European countries that receive Russian gas and may be affected by a cut in Russian supplies via Ukraine.

'Dialogue mechanism'

The letter was sent to the leaders of France, Germany, Poland, Greece, Serbia, Austria, Croatia, Slovenia, Bulgaria and Italy.

Also on the list of the recipients were Moldova, Romania, Turkey, Hungary, the Slovak Republic, Macedonia, the Czech Republic and Bosnia and Herzegovina.

Putin's spokesman Dmitry Peskov said: "The letter proposes the establishment of a dialogue mechanism. Let us hope that it will be formed and start working."

Putin said any cut in gas supplies would be an "extreme measure," urging the EU countries to immediately hold talks at the level of ministers of economics, finances and energy.

"We must lose no time in beginning to coordinate concrete steps," he said.

Previous Russian support

In his letter, Putin delivered a rebuke to the European Union, saying Brussels used Ukraine only as a source of mineral resources and has not helped the struggling ex-Soviet country financially.

In contrast, he said, Russia has over the past four years has been subsidising Ukraine's economy by discounting natural gas prices to the tune of more than 25 billion euros ($35 billion).

"What about the European partners?" he said. "Instead of offering Ukraine real support, there is talk about a declaration of intent. There are only promises that are not backed up by any real actions."

The appeal comes after Putin during a government meeting on Wednesday warned that Russia may begin requiring advance payment for natural gas from Ukraine.

(VoR, RIA Novosti, AFP)