Majority Leader Harry Reid, D-Nev., made the announcement Monday evening, telling senators, "I think what you need to do is make sure the president has the opportunity to speak to all 100 senators and all 300 million American people before we do this."
Reid had just hours earlier announced that he was scheduling lawmakers' first vote on the war resolution for Wednesday, and he claimed Monday that he had the 60 votes needed to advance the bill in the Senate. But Reid changed course amid mounting Democratic opposition to a military strike, coupled with what President Obama is calling a potential "breakthrough" deal that could avoid military action entirely if Syria agrees to surrender its chemical weapons to international authorities.
"I've talked to all my Democratic senators and we have enough votes to get cloture," Reid said. "But I don't think this is a counting numbers thing tonight."
A growing number of Democrats have come out against the resolution, which would give the president 60 days to launch air strikes against the regime of Syrian President Bashar al-Assad in retaliation for an Aug. 21 chemical attack outside Damascus.
The president is scheduled to talk privately with both Republicans and Democrats in separate meetings on Tuesday, followed by a prime-time address to the nation that evening.
Democrats say it was Obama's threat of a military strike that ultimately forced Russia and Syria to propose a diplomatic solution in which Syria would avoid a strike by giving up the chemical weapons it is accused of using against its own people.
"That we have reached this point," Senate Majority Whip Dick Durbin, D-Ill., "has more to do with a president determined to stand up as a matter of principle more than anything else."