Senators on Wednesday blocked a Republican push to tie Iran's support of terrorism to a final deal on the country's nuclear program.

Senators voted 45-54 on the amendment from Sen. John BarrassoJohn Anthony BarrassoIf Democrats want gun control, they must first concede defeat Conway: Republican concerns about gun reform 'all reconcilable' Five proposals Congress is eyeing after mass shootings MORE (R-Wyo.), which would have required President Obama to certify as part of a diplomatic deal that Iran hasn't carried out or directly supported an act of terror against the United States or a U.S. citizen.

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Sen. Ben CardinBenjamin (Ben) Louis CardinAmerica is in desperate need of infrastructure investment: Senate highway bill a step in the right direction Financial aid fraud is wrong — but overcorrection could hurt more students Democrats denounce Trump's attack on Cummings: 'These are not the words of a patriot' MORE (D-Md.) said ahead of the vote that Barrasso's amendment was a "poison pill" for the legislation. The White House had warned it would not accept such a provision, and it was stripped from an earlier version of the legislation.

The Maryland Democrat, who is ranking member of Foreign Relations Committee, said the problem with the amendment, and those like it, is that it goes "beyond the terms of the nuclear agreement.

Barrasso countered that it was "important" to reinsert the terrorism measure, which was removed as part of an agreement between Cardin and Corker.

"I think it's very important that the American people get regular certifications from the president on this important point," he said. "Congress and the American people need to know if Iran is directly supporting acts of terrorism against our country and our people."

Roughly a dozen Republicans, including Majority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellDavid Axelrod after Ginsburg cancer treatment: Supreme Court vacancy could 'tear this country apart' Pelosi asks Democrats for 'leverage' on impeachment Democrats press FBI, DHS on response to white supremacist violence MORE (Ky.), presidential hopeful Sen. Marco RubioMarco Antonio RubioGOP group calls on Republican senators to stand up to McConnell on election security in new ads What the gun safety debate says about Washington Trump moves forward with F-16 sale to Taiwan opposed by China MORE (Fla.) and Corker, huddled on the floor during the vote.

The senators at one point realized they were being watched by reporters, with Sen. John ThuneJohn Randolph ThuneSchumer blasts 'red flag' gun legislation as 'ineffective cop out' Lawmakers jump-start talks on privacy bill Trump border fight throws curveball into shutdown prospects MORE (R-S.D.) turning around and gesturing to the press gallery.

It's unclear what the meeting on the floor was about. Sen. James Risch (R-Idaho) told reporters after the vote, "We were talking about the details of the bill; that was pretty obvious wasn't it?"

He added, "It was about various aspects of the bill. ... We all have questions about it."

Asked if senators were trying to convince Rubio to stand down on his amendment that would link Israel's right to exist to the bill, Risch said, "There was nobody trying to get anybody to do anything."

Cardin blocked Rubio from bringing up his amendment.

Rubio didn't respond to questions from reporters.