WASHINGTON — President Obama on Monday tentatively embraced a Russian diplomatic proposal to avert a United States military strike on Syria by having international monitors take control of the Syrian government’s chemical weapons. The move added new uncertainty to Mr. Obama’s push to win support among allies, the American public and members of Congress for an attack.

In a series of television interviews with six cable and broadcast networks, Mr. Obama capped a remarkable day of presidential lobbying for military action and a dizzying series of developments at home and abroad. Sergey V. Lavrov, the Russian foreign minister, said early Monday that Syria could avoid an attack by putting its chemical weapons in the hands of monitors and agreeing to ultimately eliminate its massive arsenal of poison gas. It was an idea that was quickly praised by top officials in Syria and some lawmakers in the United States.

“It’s possible,” Mr. Obama said on CNN of the Russian proposal, “if it’s real.”

Mr. Obama’s statements about the haphazardly constructed plan appeared to offer him an exit strategy for a military strike he had been reluctant to order, and it came as support on Capitol Hill for a resolution authorizing force was slipping. Even some lawmakers who had announced support for it reversed course.

Senator Harry Reid of Nevada, the majority leader, said Monday evening that he would not force an initial vote on the resolution on Wednesday, slowing Senate consideration until at least next week. Democrats said they had enough votes to overcome a filibuster but possibly not enough to pass it.