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The United States Senate on Wednesday rejected an effort to tie sanctions relief for Iran under an international nuclear agreement to a requirement that President Barack Obama certify that Tehran is not supporting acts of terrorism against Americans, Reuters reported.

A handful of Republicans joined Senate Democrats to reject by a 54-45 vote a proposed amendment offered by Republican Senator John Barrasso that would have added the terrorism clause to a bill subjecting an international nuclear agreement to review by the U.S. Congress, according to the news agency.

The Senate has been engaged in intense debate over the legislation, a compromise version of the bill reached in the Senate Foreign Relations Committee last week in an effort to avoid a presidential veto.

Senators Bob Corker and Ben Cardin, the committee's Republican chairman and top Democrat, have been arguing against so-called “poison pill amendments” seeking to toughen the Iran Nuclear Review Act.

They insist that those amendments would kill its chances of becoming law by alienating Democrats and provoking a veto from Obama, who considers tougher restrictions a threat to ongoing nuclear negotiations between Iran and six world powers.

"We should do everything we can to make sure we have a voice," Corker said in the Senate on Wednesday, as he appealed to lawmakers not to push forward with partisan amendments.

Both of the amendments that have come up so far have been rejected.

The measure voted down on Wednesday sought to reinstate a clause that was removed last week as Democrats and Republicans worked out the compromise version of the bill.

Discussion of the legislation comes as Iran and the West continue talks on a permanent nuclear deal, after reaching a framework earlier this month.

Tensions arose after the preliminary framework was reached, as Iran recently accused the United States of "fraud" and "psychological warfare" in publishing a fact sheet announcing what the U.S. claims was agreed on in the framework deal and which an Iranian official called a false translation.

Secretary of State John Kerry said on Monday that the world is "closer than ever" to reaching a comprehensive nuclear deal with Iran, but warned that work on a deal is far from over and that key issues remain unresolved.

Iranian President Hassan Rouhani has dismissed possible pressure from Congress over the deal, saying the disputes between the Obama administration and Congress are an "internal issue".