The Senate has turned back an attempt to elevate any nuclear deal with Iran into a treaty, requiring a two-thirds vote to ratify.
The Republican-sponsored measure failed on a 39 to 57 vote in the GOP-controlled Senate.
The vote reflected a bipartisan effort to prevent controversial amendments that senators worry would sink a bill that would give Congress a chance to review and possibly reject a deal.
The ballot came just hours after former Secretary of State Condoleezza Rice, who was national security adviser under President George W. Bush, said any Iran nuclear deal is an executive agreement that doesn't need to be a treaty.