Meanwhile, a cease-fire is mostly holding in eastern Ukraine, limiting casualties and vastly increasing pressure on President Petro O. Poroshenko of Ukraine, who so far has been unable to deliver the increased autonomy for the pro-Russian regions of Donetsk and Luhansk that was called for in the truce agreement brokered by France and Germany.

The subtle shift by the Obama administration reflects a pragmatic recognition that the policy of isolating Russia, economically and diplomatically, is failing, analysts say.

“Americans realized that sanctions against Russia did not quite work,” Viktor A. Kremenyuk, deputy director of the Institute of the U.S.A. and Canada, a research organization that is part of the Russian Academy of Sciences, said in an interview with Svobodnaya Pressa, a news site here.

“They thought Russia had become so much a part of the world market and depended on it so much that it would be enough to frighten Moscow a little to make it surrender,” Mr. Kremenyuk said. “In reality, it’s all different. Russia not only withstood sanctions but even introduced countersanctions and demonstrated that it is not going to turn off this road.”

He added: “The U.S. cannot simply capitulate. This is why the policy change begins with statements like, ‘We shall think,’ ‘We shall assess the situation.’ In fact, this is a cautious departure from the policy of sanctions.”

To be sure, the United States position on Ukraine has not shifted, and Mr. Kerry said at a news conference in Sochi that he had “made clear our deep concerns” including about Russia’s “continued arming, training, command and control of separatist forces.” The administration portrayed the visit as intended to explore new avenues of collaboration, especially in Syria, and Mr. Kerry in his remarks again insisted that Russia and Ukraine fulfill the terms of the cease-fire accord signed in Minsk, Belarus.

For the Russian news media and political pundits, however, it was striking that Mr. Kerry’s arrival came three days after Moscow’s huge celebration of the 70th anniversary of the Allied victory over Nazi Germany — an event that the United States refused to attend and had urged other nations to shun as well.