The Republicans on Tuesday once again made an unsuccessful attempt to muster the 60 votes needed to reject the Iran agreement in the Senate, The Hill reported.
The Senate voted 56-42 for the Iran resolution, short of the 60 votes needed to move forward.
However, the Republicans plan to take on the agreement on Thursday for the third time, hoping to change the Democrats’ vote.
Senate Majority Leader Mitch McConnell declared after Republicans’ second fiasco on Tuesday that the "debate will continue”.
"A strong, bipartisan majority of the House of Representatives voted to reject the deal. A strong, bipartisan majority of the Senate would vote to reject the deal too," McConnell said.
"If only Democrat senators would stop blocking the American people from even having a final vote on one of the most consequential foreign policy issues of our age,” he added.
It was the second time in less than a week that Democrats safeguarded the Iran agreement.
42 Democrats voted on Thursday in favor of the agreement and prevented a resolution disapproving the deal.
Under a law Obama signed in May, Congress has a 60-day period ending on September 17 to pass a resolution disapproving of the July 14 agreement.
If such a resolution were to pass, and survive Obama's promised veto, it would bar the president from waiving many US sanctions on Tehran, a key component of the nuclear deal.