The U.S. and European Union have reached “crunch time” to halt further destabilization in Ukraine and curb any further Russian expansion in the region.

Prospects for a negotiated end to the crisis were set back after camouflaged gunmen fired on government forces near Slovyansk, about 240 kilometers (150 miles) from the Russian frontier in eastern Ukraine. One serviceman was killed and five were wounded, with an unknown number of casualties on the separatist side, Interior Minister Arsen Avakov said on Facebook.

“Henchmen” of the Kiev government with the backing of Western nations are organizing terror attacks, Russia’s Ambassador to the United Nations Vitaly Churkin said at an emergency session of the UN Security Council in New York.

Russia “is spreading fiction -- we must stop this tonight,” U.S. Ambassador to the United Nations Samantha Power said at the meeting. “Insecurity in Ukraine is written and choreographed by Russia,” she said.

The U.S. backed Ukraine’s accusation that Russia was behind the violence. Yet the repeated threat of additional sanctions directly targeting Russia’s economy hasn’t prevented such clashes and there’s little likelihood of a military response, according to analysts.

“This is crunch time for the West’s response to Russia’s attempts to assert its influence over eastern Ukraine,” said Nicholas Spiro, founder of Spiro Sovereign Strategy in London. “This is supposed to be the trigger for more meaningful economic and trade sanctions against Russia. We’re now going to see the extent to which the West is unified in its willingness to face down Russia.”

David Fuller's view

The policy for curbing Putin’s expansion in Ukraine and potentially other parts of Eastern Europe would be increasingly tough economic sanctions, signalled in advance.  However, Putin is gambling, probably correctly, that neither the EU nor the USA has much appetite for extending economic measures which would also hurt their own economies.  

Therefore, the Ukraine is effectively at Putin’s mercy and he is very likely to extend Russia’s influence, not only in the Eastern region but also by destabilising the political regime in Kiev.  Other East European countries will obviously take note and lose confidence in the West’s ability to help them.  This problem will drag on, short of intervention within Russia to stop Putin from recreating a pariah state.