The Kremlin declared its plans hours after the United Nations mediator, Staffan de Mistura, met with the Syrian government delegation in Geneva.

There have been growing signs of differences between Russia and the Syrian government over the Geneva talks, which Moscow has pressed hard for, along with Washington. And for Mr. Assad, the prospect of Russia’s leaving him to fend for himself is sure to focus his mind on following its lead — advice that Russian officials have publicly offered him in recent days.

“I seriously doubt Moscow is breaking with Assad,” said Andrew J. Tabler, a scholar on Syria at the Washington Institute for Near East Policy. Rather, he said, the Russian announcement appeared to be “putting the military burden back on Assad so as to soften up his negotiating position.”

Moscow has recently evinced a measure of frustration. Three times in the past two weeks, Mr. Assad and his advisers have made public statements noticeably out of sync with Russia’s declared goal of substantive talks — most recently on Saturday, when Foreign Minister Walid al-Moallem of Syria declared that Mr. Assad’s rule was a “red line” and that there would be no discussion of presidential elections.

Image President Vladimir V. Putin of Russia. Credit... Michael Klimentyev/Agence France-Presse — Getty Images

Speculation about Russia’s announcement grew so intense, including among Syrian government loyalists on social media, that by Monday night, Mr. Assad’s office issued a statement to dispel rumors that the president had been caught flat-footed. It blamed “partners in Syrian bloodshed” for the conjecture and said that the announcement had been made “with full coordination” after “extensive study” of recent military successes and that “Syria and Russia are, as always, together fighting terrorism.”

The Russian move may also be a reflection that Mr. Putin is now supremely confident in Mr. Assad’s renewed stability and can afford to step back a bit and play statesman.