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 BarrassoHouse votes to block drilling in Arctic refuge Lobbying World Meet the Democratic senator trying to negotiate gun control with Trump 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.

Republican Sens. Lamar AlexanderAndrew (Lamar) Lamar Alexander The 13 Republicans needed to pass gun-control legislation Liberal group urges Senate panel to vote against Scalia as Labor secretary Suburban anxiety drives GOP on guns MORE (Tenn.), Dan CoatsDaniel (Dan) Ray CoatsCongress should defy Dan Coats' last request on phone surveillance America's cyber blind spot 2020 Democrats raise alarm about China's intellectual property theft MORE (Ind.), Bob CorkerRobert (Bob) Phillips CorkerTrump announces, endorses ambassador to Japan's Tennessee Senate bid Meet the key Senate player in GOP fight over Saudi Arabia Trump says he's 'very happy' some GOP senators have 'gone on to greener pastures' MORE (Tenn.), David Perdue (Ga.), Jeff FlakeJeffrey (Jeff) Lane FlakeFlake donates to Democratic sheriff being challenged by Arpaio in Arizona The Hill's Morning Report - Trump says US-China trade talks to resume, hails potential trade with Japan, UK Joe Arpaio to run for Maricopa County sheriff in 2020  MORE (Ariz.), Lindsey GrahamLindsey Olin GrahamThe Hill's Morning Report - Trump takes 2020 roadshow to New Mexico Bolton exit provokes questions about Trump shift on Iran The 13 Republicans needed to pass gun-control legislation MORE (S.C.), Orrin HatchOrrin Grant HatchTrump to award racing legend Roger Penske with Presidential Medal of Freedom Trump awards Presidential Medal of Freedom to economist, former Reagan adviser Arthur Laffer Second ex-Senate staffer charged in aiding doxxing of GOP senators MORE (Utah) and John McCainJohn Sidney McCain The 13 Republicans needed to pass gun-control legislation Biden's debate performance renews questions of health At debate, Warren and Buttigieg tap idealism of Obama, FDR MORE (Ariz.) voted with Democrats against the amendment.

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Sen. Ben CardinBenjamin (Ben) Louis CardinCongress passes bill to begin scenic byways renaissance GOP lawmaker: 'Dangerous' abuse of Interpol by Russia, China, Venezuela Senators pressure Trump to help end humanitarian crisis in Kashmir 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 McConnellThe Hill's 12:30 Report: NY Times story sparks new firestorm over Kavanaugh Senator asked FBI to follow up on new information about Kavanaugh last year Congress must reinstate assault weapons ban MORE (Ky.), presidential hopeful Sen. Marco RubioMarco Antonio Rubio The 13 Republicans needed to pass gun-control legislation GOP group's ad calls on Graham to push for election security: 'Are you still trying?' Former Massachusetts Gov. Deval Patrick joins CBS News as contributor 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 ThuneTrump, lawmakers consider app that would conduct background checks: report 'Mike Pounce' trends on Twitter after Trump slip at GOP retreat The Hill's Morning Report — Biden steadies in third debate as top tier remains the same 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.