The long-awaited truce in eastern Ukraine appears to be taking hold, with Ukraine's army reporting no combat fatalities for the first time in weeks. (Reuters)

Russia shifted its showdown with Ukraine to economic pressure on Wednesday, as Russian President Vladimir Putin threatened to cut off natural gas within days even as fighting finally started to quiet in war-torn eastern Ukraine.

Putin’s warning raised new troubles for Ukraine’s economy, which is on the verge of collapse. Among the problems: dangerously low reserves of foreign currency needed to pay for the critical natural gas supplies.

Putin also said that any cutoff could also hit Europe, raising the prospect that the continent could again face shortages with warmer weather still months away.

Ukraine is a vital throughway for Russian gas deliveries to Western Europe. Russia has in the past cut off gas to nations with which it was having geopolitical disputes, although it has always denied using energy as a weapon.

The tough line by Russia underscores its growing tensions with the West during the nearly 11-month uprising in eastern Ukraine by pro-Moscow rebels.

Ukraine’s Western-backed government and its allies claim Russia has sent troops and weapons to aid the separatists in Europe’s bloodiest conflict since the Balkan wars of the 1990s.

Russia strongly denies the charges but has been a key political voice for the rebels — with significant influence over their adherence to a cease-fire pact reached earlier this month.

“We hope that things won’t get as far as these extreme measures and that the gas supply won’t be interrupted,” Putin said Wednesday. “But this doesn’t depend on us alone. It depends on the financial discipline of our Ukrainian partners.”

“Naturally this might create a certain threat for gas transit to Europe,” he added.

[Related: Can U.S. natural gas rescue Ukraine from Russia?]

The energy dispute stems in part from gas supplies to territories of eastern Ukraine held by pro-Russian rebels.

Rebel leaders say that they have been cut off by Kiev, although Ukrainian government authorities deny it. Russia, in turn, has started to deliver energy directly to the breakaway territories, and it is charging Ukraine for the service.

The cutoff of gas to eastern Ukraine, Putin said, “smells of genocide” given the bleak conditions there.

Russia says that Ukraine has paid for only three to four more days of delivery.

The new tussling over gas came on the first day in several weeks in which no Ukrainian soldiers were killed on the front lines, a military spokesman said. Rebel leaders also said that the conflict had largely quieted.

Both sides agreed to a cease-fire starting Feb. 15, but in the days that followed, fighting grew fiercer near the crucial Ukrainian-held railway hub of Debaltseve. Kiev surrendered the town last week in a chaotic retreat.

Nearly 5,800 people have died in the fighting, according to U.N. estimates, and more than 1 million people have been displaced from their homes.

As the violence has calmed, Ukraine’s economic problems have worsened.

Ukraine’s currency has been shedding value against the dollar, and policymakers in recent days have imposed strict limits on foreign currency transactions in the hopes of stanching the losses. A weakened currency makes everything from energy to weapons to food more expensive for the Ukrainian government and its citizens.

The currency has lost more than 40 percent of its value this month alone.

[Related: Can Europe wean itself from Russian natural gas?]

Ukrainian policymakers say they need up to $40 billion in assistance. And although Western nations have promised aid, it has been slow in coming, a stark signal to Ukraine that it may be largely on its own against its far more powerful neighbor.

Ukrainian Finance Minister Natalie Jaresko said Wednesday that the heads of the International Monetary Fund would meet March 11 to decide whether to approve new loans to the troubled country. But that suggests Ukraine will be left to scrape by until then, and possibly longer.

Russia has sought to exploit splits in the Western response to the conflict, and on Wednesday Putin met in Moscow with Cypriot President Nicos Anastasiades to sign cooperation agreements that again highlighted European disunity.

Cyprus, an European Union member, has long been a Russian banking haven, and it took Russian financial support during its 2013 financial crisis. Anastasiades has opposed further E.U. sanctions against Russia even as others in Europe are raising the prospect of more.

The Russian and Cypriot foreign ministers on Wednesday signed an agreement to allow Russian naval ships to dock at Cypriot ports. The deal was a stark sign of the differences of opinion in Europe about how to handle Russia, since other Western nations have boycotted any military cooperation with Russia.

Also Wednesday, a Russian investigative newspaper published a document that it said suggested that the Kremlin had been advised to annex Ukraine’s Crimean Peninsula and foment separatist strife even before Ukraine’s Russian-allied president, Viktor Yanukovych, fled office on Feb. 22, 2014.

“It seems to be correct and appropriate to play on the centrifugal aspirations of various regions of the country . . . to initiate the annexation of its eastern regions to Russia,” the document said, according to Novaya Gazeta, an opposition newspaper.

There was no immediate confirmation of the document’s authenticity nor of its function within the Kremlin, where it was “brought” sometime between Feb. 4 and Feb. 12, 2014, the newspaper said. A Kremlin spokesman denied knowledge of the document.

The step-by-step recommendations closely predict what was later to come in Ukraine. The Kremlin has previously said it acted without premeditation to secure Crimea because it feared for the safety of Russian-speakers in the aftermath of Yanukovych’s departure.