Russian President Vladimir Putin. (Alexei Druzhinin/Sputnik/Kremlin/Reuters)

PRESIDENT OBAMA and some of his senior aides are sounding skeptical about the partial cessation of hostilities due to begin in Syria on Saturday, and for good reason. Russian President Vladi­mir Putin has agreed to multiple cease-fires in Syria and Ukraine over the past two years but has observed none of them. The same is true of Syrian dictator Bashar al-Assad, who hasn’t bothered to hide his intention to continue slaughtering his own people. If some slackening in the fighting actually takes place, and humanitarian convoys get through, it will be because Mr. Putin found it was in his strategic interest. That is the real import of the cease-fire: It puts Russia in control of what happens next in Syria.

For now, Mr. Putin is reveling in the geopolitical victory handed to him by the Obama administration, which, rather than support Syrian rebels against Russia’s bloody assault on the areas they hold, chose to sue for peace on Moscow’s terms. The Russian ruler has been making phone calls to everyone from Mr. Obama to the leaders of Israel and Saudi Arabia, while crowing on television over Russia’s leading role — with the United States as a junior partner — in sorting out the Middle East. No doubt Mr. Putin hopes that this demonstration of his importance, and perhaps a relenting of Russian raids on hospitals and other civilian targets in northern Syria, will prompt a few governments to press for the lifting of European Union sanctions on his regime — even though he is violating the cease-fires he agreed to in Ukraine.

Russia also has the option of continuing its military campaign against the Syrian rebel base in the city of Aleppo, while claiming to respect the cessation of hostilities. That’s because the terms of the deal negotiated by Secretary of State John F. Kerry exclude the extremist group Jabhat al-Nusra, some of whose fighters are in Aleppo along with Western-backed rebels. The Assad regime, for its part, has insisted it will continue operations against all “terrorist” groups, which it defines as any that have taken up arms against the regime. It has meanwhile scheduled parliamentary elections for April, in blatant disregard of the plan for Syrian peace promoted by Mr. Kerry and nominally accepted by Russia.

Mr. Kerry said during a congressional hearing this week that the administration is considering a “Plan B” if the cease-fire fails. Some senior national security officials are said to be deeply resistant to falling in behind Mr. Putin — as they should be. But as The Post’s Karen DeYoung reported Thursday, there’s no consensus on taking significant measures to push back against continuing Russian military action, such as by supplying rebels with antiaircraft weapons. Some are calling for new economic sanctions on Moscow, but Mr. Obama has been reluctant to act on those without support from Europe.

It is, of course, this very passivity in U.S. policy that empowers Mr. Putin to act as he chooses in Syria. For the sake of the hundreds of thousands of people bottled up in Aleppo and other places subjected to sieges and bombing, we can hope that he concludes that a pause in military operations is in his interest. But if he does so, it won’t be because his actions have been constrained by the United States.