WASHINGTON — (CNN) For the second time in two weeks, Senate Democrats Tuesday are expected to block a Republican push for a final vote on the Iran nuclear deal, which was negotiated by President Barack Obama and is uniformly opposed by congressional Republicans.

The procedural vote, which needs support from 60 senators to pass, fell two votes shy last week.

GOP leaders hope that two of those Democrats will buckle to pressure from constituents and flip their votes.

If last week’s result holds again, it means the historic Iran deal, which lifts economic sanctions against Iran in return for it curbing its nuclear ambitions for the next several years, will be set to be implemented despite majority votes in the House and Senate against it.

In floor debate, Republicans argued that an international accord of this magnitude deserves a final up or down vote by Congress.

“Do senators think it’s right for the world’s leading sponsor of terror to be able to maintain an American-recognized nuclear program?” Senate Majority Leader Mitch McConnell asked, questioning the legitimacy of a Democratic filibuster of a resolution of disapproval against the deal.

But Senate Democratic Leader Harry Reid countered that the vote last week was evidence that Democrats support the deal because they believe it will prevent Iran from getting nuclear weapons.

“The outline he just gave has nothing to do with intellectual credibility. The agreement that was finalized last week dealt with one subject and one subject only. Whether or not Iran should have a nuclear weapon and the answer was resoundingly no,” Reid said.

Senate Republican leaders have hinted there could be more votes this week before the Thursday deadline for congressional action against the deal. The House also plans votes this week.

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