A week ago, militants seized government buildings in three eastern Ukrainian cities in what U.S. Secretary of State John F. Kerry charged was "an illegal and illegitimate effort" by Russia to "create a contrived crisis with paid operatives." Mr. Kerry threatened that the United States would respond with sanctions against Russia's mining, energy and banking sectors. But in the following days, the Obama administration failed to act, other than against a few minor figures in occupied Crimea. G7 finance ministers meeting in Washington on Thursday also could not agree on any measures.
Consequently, none of those governments should have been surprised by the broader and more audacious offensive launched in eastern Ukraine on Saturday. According to independent observers, busloads of men in camouflage uniforms carrying Russian weapons attacked government buildings in at least four more towns. On Sunday, fighting broke out as Ukrainian forces tried to retake a building in the town of Slovyansk, and casualties were reported on both sides.
Once again, senior U.S. and European officials charged that Russia was behind the attacks. Samantha Power, the U.S. ambassador to the United Nations, said the actions were "professional," "coordinated," and bore "telltale signs of Moscow's involvement." But again, there was no tangible U.S. response. Ms. Power said only that there would be a "ramping up" of sanctions "if actions we've seen over the last few days continue."
How much more action must Russia take to provoke a response? For weeks U.S. President Barack Obama has been saying a military intervention in eastern Ukraine would prompt U.S. sanctions far more consequential than the measures taken against a handful of Vladimir Putin's cronies and one bank on March 20. By the U.S. account, that military intervention is now underway. Officials say it closely resembles the quasi-covert Russian military operation that led to the annexation of Crimea.
A tough western reaction might have stopped the Russian offensive after last weekend. Now it is far more dangerous. The bloodshed reported Sunday may be taken by the Kremlin as an excuse to order a more overt invasion by the tens of thousands of troops it has massed near the border. The Ukrainian government, for its part, has rightly taken the position that it cannot allow Russia to take over its cities by force of arms without fighting back.
The Obama administration elected not to adopt significant measures last week in part because it was awaiting what it described as a diplomatic opening -- a four-way meeting this week of foreign ministers from the United States, Russia, Ukraine and the European Union. Yet there is almost no chance this gathering, if it takes place at all, can lead to an acceptable solution for Ukraine. Moscow is demanding the country be chopped up into pieces and that areas under its influence be given a veto over Ukraine's foreign policy. Given the weak response to its aggression, Moscow has no incentive to drop that scheme.
It may be too late to prevent war in eastern Ukraine. But the United States must quickly take the measures promised by Mr. Obama and Mr. Kerry, or lose what little credibility it retains on Ukraine. If Sunday's combat continues, it should also reconsider Kyiv's request for non-lethal supplies and small arms for its forces. If Ukrainians are forced to fight for their country, they should be helped.