Washington(CNN) For months, Senate aides and their bosses pored over sanctions legislation aimed at ratcheting up pressure on Iran as it negotiates the fate of its nuclear program with the U.S. and five other world powers.
The result of that redrafting process is a significantly watered-down version of the Nuclear Free Iran Act of 2013, also known as Kirk-Menendez, that addresses much of the criticism the bill faced last year. Though crafted to build increased support from previously skeptical lawmakers, it remains staunchly opposed by the White House and world leaders involved in the negotiations with Iran.
The White House is standing by its vow to veto the legislation, claiming it would undermine the chance for a diplomatic solution.
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As opposed to last year's version, the new bill cuts out the more stringent requirements that could have triggered sanctions amid talks, and would only bring down sanctions on Iran if negotiators don't reach a deal to roll back its nuclear program by the July deadline, according to a copy of bill obtained by CNN. The language could change, as it heads to the banking committee for consideration next Thursday.
The new bill would trigger sanctions starting July 6, which would continue to ratchet up every month that there is no deal. Per the legislation, Obama would only be able to prevent those new sanctions if waiving them would help achieve a comprehensive deal with Iran, and if he can certify that Iran is not moving closer to obtaining a nuclear weapon.
Last year's bill drew support from 60 senators, but never got a vote on the Senate floor because of the White House veto threat and several Democrats slowly withdrew their support.
But a Republican majority in Congress has breathed new life into the push to pass a sanctions bill.
It's also created a fiercely contentious environment that saw Sen. Bob Menendez, D-New Jersey, one of the lead authors of the bill, accuse the White House of using talking points "straight out of Tehran."
Meanwhile, the White House and opposition groups to pull out all their firepower, with Obama threatening a veto before the bill even became public. The White House maintains the bill's latest iteration would violate the spirit of negotiations with Iran, torpedo the talks and then give Iran cause to point the finger at the U.S. for failing to reach a diplomatic solution.
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"Why is it that we would have to take actions that would jeopardize the possibility of getting a nuclear deal over the next 60 or 90 days?" Obama asked at a press conference last week in which he threatened to veto a bill.
A senior congressional aide with knowledge of the legislation said the goal is to "create more positive pressure" and takes into account the year of negotiations that have passed. The bill was stripped down in recognition of Obama's veto threat, the aide said.
While the bill removed a slew of the most controversial provisions, the aide said the bill will be subject to new amendments on the Senate floor which could add more fangs to the current version or simply add more bipartisan bonafides.
The chance for additional amendments on the floor may be what prompted Sen. Mark Kirk, R-Illinois, to sign onto with the current, more stripped-down version. In an interview earlier this month, Kirk told CNN he was pushing for as few changes to his original proposal as possible, saying, "The more changes, the worse."
Among the changes, the new bill strikes language that would have required Iran to "dismantle its illicit nuclear infrastructure, including enrichment and reprocessing capabilities and facilities" in a final deal. Instead, the new bill explains that it is "the sense of Congress" that a final deal should "reverse the development" of that nuclear infrastructure.
The language is not just a softer tone, but doesn't lead to interpretations that a final deal would hold Iran to a zero-enrichment standard -- an impossible demand for negotiators to achieve.
The new legislation also removes a provision that would require President Barack Obama to certify that Iran has not supported terrorism against the U.S. or any American people or property in the world. Just this week, a U.S. embassy vehicle was fired at by Houthi rebels in Yemen who are backed by Iran.
"We worked to create a constructive piece of legislation that does not violate the Joint Plan of Action," the congressional aide said, referring to the framework for the P5+1 negotiations with Iran.
But opponents of the bill are urging Congress to lay off Iran entirely to avoid undoing the fragile international coalition needling Iran toward a final agreement. Obama bluntly told Congress to "hold their fire."
One of several Democratic lawmakers on the fence over the measure seemed willing to do just that.
"Sanctions have worked and is what got Iran to the negotiating table. The best solution is a strong diplomatic deal. The question is whether passing new sanctions now would help us get there," said Sen. Kirsten Gillibrand in a statement. "The President strongly believes it would gravely harm negotiations, and therefore, I am willing to give him more time before supporting this bill."
Kate Gould, the lead Iran lobbyist for the Quaker-founded Friends Committee on National Legislation, said she is making sure key offices are aware of the grassroots opposition. "Passing a triggered sanctions bill is playing chicken with diplomacy," Gould said. "Passing new sanctions that wouldn't take effect unless certain conditions are met may very well provoke Iranian hardliners into responding in kind."
International pressure has also been mounting on Congress, with the foreign ministers of France, Britain and Germany penning a joint editorial on Thursday opposing additional sanctions. And British Prime Minister David Cameron spent some of his time in the U.S. calling key senators to urge them to oppose the sanctions bill.
The division over the Kirk-Menendez sanctions bill is also fueling alternative efforts. Sen. Bob Corker, the newly minted chairman of the Senate Foreign Relations Committee, is pushing a bill to require congressional oversight over any eventual deal with Iran.
And partisan odd couple, Sens. Barbara Boxer, a California Democrat, and Rand Paul, a Kentucky conservative, are drawing up what they called a more "moderate" sanctions bill that would cue up legislation for the Senate to pass new sanctions if negotiations falter. Paul was one of just two Republicans to oppose the Kirk-Menendez measure last year.