A COUPLE of conclusions can be drawn from the welter of contradictory statements and actions on Ukraine by Russian President Vladi­mir Putin over the past several days. One is that Mr. Putin has no compunction about making demonstrably false statements. On Wednesday, he said he had withdrawn Russian troops massed on Ukraine’s border, but on Friday NATO’s secretary general confirmed that no such movement had been detected.

Another lesson is that, contrary to the defeatist assessments sometimes heard in Washington, Mr. Putin can be moved by sanctions. The Russian ruler’s sudden concession that Ukraine’s planned May 25 elections — which his spokesman called “absurd” — could be “a step in the right direction” can be understood only in the context of a threat by President Obama and German Chancellor Angela Merkel to impose punishing “sectoral” sanctions on Russia if it disrupted the vote. It was no accident that Mr. Putin spoke up even as a U.S. delegation was holding talks in Europe on the details of those sanctions.

Mr. Putin’s statements and his seeming openness to mediation by the Organization for Security and Co-operation in Europe are of a piece with his agreement three weeks ago to a “de-escalation” plan for Ukraine — following which Russia “fulfilled none of its commitments,” as Assistant Secretary of State Victoria Nuland told Congress on Thursday. If he can deflect threatened sanctions or sow dissension among Western governments with words, Mr. Putin will do so.

But the words have no relation to Russia’s actual behavior. On the ground, all evidence suggests that Moscow is still backing armed militants in eastern Ukrainian cities, seeking to undermine the elections and aiming at imposing its rule, directly or indirectly, on as much of the country as possible. Mr. Putin’s triumphant appearance in Sevastopol, Crimea, on Friday showed that his aim is to manipulate the West into tolerating and eventually accepting his illegal aggression.

The response to this cynical gamesmanship must be twofold. First, the Obama administration and its European allies must judge Mr. Putin according to outcomes in Ukraine, not words. If pro-Russian forces go ahead with a “referendum” on Sunday on separating from Ukraine, that will show Mr. Putin’s true position; with its special forces operating in the region, Moscow could stop the initiative if it chose to. Similarly, if the May 25 elections are blocked or disrupted in Donetsk, Luhansk or Odessa, Mr. Putin should be held responsible, regardless of his rhetoric.

The other way to counter Mr. Putin is to treat sanctions and diplomacy not as alternative paths but as necessary complements. The Russian ruler is more likely to compromise if sanctions continue to escalate; that’s why it is important that a European Union meeting scheduled for Monday results in additional steps. Though Mr. Obama and Ms. Merkel linked steps against Russian industry and finance to the May 25 elections, the West must be ready to adopt some of those measures sooner if Russian-backed separatists do not back down from their vote.

The world will know Mr. Putin is serious about accepting an independent Ukraine when he pulls his special forces out of the east and Russian troops withdraw from the border. For now, they are still very much there.