As expected, Senators fell two votes shy of the 60 needed to advance a resolution disapproving of the international accord, meaning the legislation aimed at sabotaging the deal is essentially dead.
"The Senate has spoken with a clarion voice and declared that the historic agreement to prevent Iran from obtaining a nuclear weapon will stand," Senate Minority Leader Harry Reid said after Democrats cleared the way for the accord.
The result effectively assures that the deal, in which Iran has agreed to roll back its nuclear program in exchange for an easing of crippling economic sanctions, will go into force while sparing Obama the embarrassment of having to use his veto pen against a resolution of disapproval.
But Republicans, who unanimously oppose the accord, vowed to keep fighting, with House Speaker John Boehner insisting "this debate is far from over, and frankly it's just beginning."
Boehner said House Republicans will "use every tool at our disposal to stop, slow and delay this agreement from being fully implemented," including suing the president to prevent him from carrying out the Iran accord.
"That is an option that is very possible," Boehner told reporters Thursday.
Congress had passed legislation that gave it 60 days to review the July accord, and play the "spoiler" role if it deemed the agreement was not in the security interests of the United States.
That 60-day period expires on September 17.
"That will be good news, and it will mean that the international community can move forward with implementing the agreement," White House spokesman Josh Earnest said Thursday in anticipation of the Senate vote.
The deal struck between Iran and six world powers provides Tehran relief from crippling economic sanctions in exchange for limits on its nuclear program.
Republicans complain the deal does not do away with the program altogether, fails to provide for spot inspections of nuclear sites or force Iran to end support for militant groups like the Palestinian Islamist movement Hamas.