In a bid to reassure Eastern European nations that they enjoy full military protection from the spillover effects of the worsening crisis in Ukraine, US Vice-President Joe Biden has announced he will soon visit Romania for an unprecedented second tour to the region in as many months.
The announcement delighted Romania's leaders: Prime Minister Victor Ponta hailed the "excellent security cooperation" between the two countries. But the move heightened Russia's hostility towards its neighbour, with senior officials in Moscow warning Romania of "a very harsh" response.
The showdown between Russia and Romania is now rapidly growing into a broader European confrontation.
Traditionally, it was Poland which attracted most of Russia's anger, because the Poles persistently pushed for Ukraine's integration into the West. However, Poland's longstanding role as Russia's regional bogeyman is now being replaced by Romania, Eastern Europe's second-biggest nation, a country with its own historic difficulties with Russia.
The Republic of Moldova, sandwiched between Romania and Ukraine, was created by the Soviet Union at the end of World War II on land seized from Romania; the Romanians also lost another chunk of their territory which is now incorporated into Ukraine.
All three - Ukraine, Romania and Moldova - are not interested in reviving their old historic quarrels or revising existing borders. Still, none of them knows what to do with Transnistria, a sliver of land which belonged to Moldova, but is now controlled by ethnic Russian separatists.
The manner by which ethnic Russians created Transnistria two decades ago is identical to the way Russian separatists are now carving up bits of territory out of Ukraine: seizures of public buildings and the formation of paramilitary forces which rely on Russian military support to create virtual new states.
But as Transnistria has no territorial continuity with Russia, the enclave was long regarded as one of Europe's "frozen conflicts", flashpoints which are never resolved but do not flare up either.
No longer. At the end of last week, Russia dispatched Deputy Prime Minister Dmitry Rogozin to Transnistria. The ostensible reason for his visit was to attend a military parade marking the anniversary of the defeat of Nazi Germany in World War II.
In practice, however, Mr Rogozin's presence was seen as a signal of Russia's renewed interest in Transnistria, with a view to its possible annexation into Russia, should eastern Ukraine, which borders the enclave, fall into Russian control as well.
And Mr Rogozin did nothing to dispel these fears. He reassured local Russians that Moscow "will not allow them to be isolated", and spoke openly of the ethnic Russians' "right to self-determination", even if this results in Moldova's carve-up.
More significantly, Mr Rogozin was embroiled in a spat with Romania, which refused to allow his plane through Romanian airspace, forcing the Deputy Premier to take a commercial flight instead.
In response, a furious Mr Rogozin tweeted in English that the next time he visits the region, "I'll fly on board TU-160", Russia's largest strategic bomber.
The initial instinct in European capitals was to ignore the veiled military threat. Mr Rogozin, who is responsible for his country's armaments industries, is famous for his outlandish behaviour and aggressive language.
But this time, he appears to enjoy the full support of his superiors: On his return home, he was received by Russian Prime Minister Dmitry Medvedev, who vowed that Moscow would "take the incident into account" in all its future economic dealings with both Moldova and Romania.
But while Romania is being kept in the doghouse, Russia is expanding its relations with Hungary and Bulgaria, in a clear attempt to prevent a coherent response from Ukraine's Eastern European neighbours.
The Hungarians, who have a large ethnic Hungarian minority in Ukraine which they wish to safeguard, are keen to remain on good terms with Russia. And Bulgaria, the European Union's poorest nation, needs economic ties with Russia.
A German intelligence report leaked to Spiegel, the German news weekly, claims that Bulgaria has been transformed into "Russia's bridgehead" in Europe.
Ironically, some Europeans make the same accusation against Germany itself.
With the EU still scrambling to reach a unified position on Russia, it falls to the Americans to shoulder the burden: Washington quickly dispatched the deputy director of the Central Intelligence Agency, Ms Avril Haines, to Romania in the hope that this would steady local nerves. It also serves as a none-too-subtle hint that Washington will not tolerate further Russian encroachments or bullying in Eastern Europe.
But as European diplomats ruefully acknowledge, Russia continues to retain the initiative in the region, and has every intention of using it.
This article was published on May 14 in The Straits Times.
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