Russian President Vladimir Putin said he "did not consider" the possibility of annexing Crimea. Then he annexed it.

Since then he has said: "We do not want to divide Ukraine; we do not need that."

But the Russian military has massed forces at Ukraine's borders. And Russia's government has enacted punitive economic actions against Ukraine, including raising the price of gas, demanding loan repayment and shutting its border to imports from Ukraine.

Mr. Putin, in the same speech that offered unconvincing assurances about not wanting to divide Ukraine, called Kiev, its capital, "the mother of all Russian cities."

In other words, when Mr. Putin says he has no intention of grabbing more territory, watch out. His disclaimer of any further land-grabbing in Ukraine beyond Crimea would also be more credible if the Russian media - now largely dominated by Mr. Putin's sycophants - began reporting truthfully about Ukraine's new government.

Instead, Mr. Putin's mouthpieces portray it as full of, to use his own words, "neo-Nazis, Russophobes and anti-Semites" who had launched a "coup" against Ukraine's president (and Putin ally) Viktor Yanukovich.

The truth is that Mr. Yanukovich voluntarily fled the country even though the opposition had agreed with him on a plan for elections to replace him. He did not wait out the inevitable protests, but swiftly left office.

It is clearly Mr. Putin's intention to keep the threat of further annexation alive despite his assertions to the contrary. The last time Europe saw this kind of ethnic-based assault on international law and national sovereignty was when Serbia set out to redraw the map of the Balkans in the early 1990s under Slobodan Milosevic, who died in prison in 2006 while being tried in The Hague for war crimes.

By comparison, Mr. Putin has exercised military restraint - so far.

And so far, the Western response has been comparatively muted, including a punitive tit-for-tat on mild economic sanctions.

Yes, President Barack Obama and other Western leaders have called off June's planned G-8 summit in Sochi, Russia. Instead, they announced Monday that they hold a G-7 summit - minus Russia - in Brussels this summer.

And President Obama, in a speech delivered in Brussels Wednesday, correctly warned that the U.S. and Europe must stand together against Russia's reversion to "the old way of doing things" - as in seizing territory through the threat or use of military force.

As President Obama explained, if Russia's aggression is rewarded: "That message would be heard not just in Europe, but in Asia and the Americas, in Africa and the Middle East."

On Thursday, President Obama called on Mr. Putin "to move back those troops and to begin negotiations directly with the Ukrainian government, as well as the international community."

Such blunt talk is welcome.

Unfortunately, identifying the problem doesn't solve it. Mr. Putin knows there's no realistic expectation of a U.S. or NATO military response to his aggression.

There's also no guarantee that stronger economic and diplomatic sanctions will deter Mr. Putin over the short term.

But the best chance of limiting his long-term expansion ambitions remains a united front by President Obama and the leaders of other Western powers.

And they should have no illusions about Mr. Putin's intentions - and put no faith in his word.