The US Senate on Tuesday rejected an effort to require an international nuclear agreement with Iran to be considered a treaty, which would have forced any deal to be approved by two-thirds of the Senate's 100 members before it could take effect.
The Senate voted 57-39 to reject the measure, offered as an amendment to a bill requiring an Iran nuclear deal to be reviewed by the US Congress, Reuters reported.
The amendment would have needed the support of 60 senators to pass, but its support from 39 Republicans showed that there could be intense debate in the coming days as the Senate agrees on a final version of the legislation.
Senator Majority Leader Mitch McConnell and other members of the chamber's Republican leadership were among those who supported the amendment, despite an emotional appeal against it from Senator Bob Corker, the Republican chairman of the Senate Foreign Relations Committee and author of the Iran Nuclear Review Act.
McConnell had said earlier in the day that he wanted to pass a "sensible" bipartisan bill but made it clear that he expected lawmakers to introduce a wide variety of amendments to the legislation.
"I still expect to see a vigorous debate this week. I still expect to see a robust amendment process," he said in a Senate speech before debate on the bill.
The Senate foreign relations panel voted 19-0 last week for a compromise version of the Iran Nuclear Review Act.
But some US Republicans have introduced amendments seeking to toughen the bill, raising the possibility of a partisan battle that could complicate the measure's chances of passing.
Before the compromise, US President Barack Obama had threatened to veto the bill, saying that some of its provisions threatened delicate international negotiations with Iran.
