Politics and nuclear-nonproliferation policy making are sometimes an explosive combination. Senator Bob Corker (R-Tenn.) and five Republican Senators, along with six Democrats have introduced legislation they are selling as a simple up-or-down vote on a possible agreement between the P5+1 and Iran that would verifiably constrain that country’s worrisome nuclear program.

A closer look at the Corker bill, S. 615, reveals it is more than a simple up-or-down vote. The bill is an unhelpful initiative that could complicate the delicate P5+1 and Iran talks at a critical juncture.

It could also provide an opportunity to those partisans on the Hill who want to blow up the effective diplomatic solution that the majority of the U.S. public says it wants. Without this agreement, the risk of an Iran nuclear crisis will escalate, the risk of a military conflict would grow, and chances of a nuclear-armed Iran would increase.

Yet the unprecedented March 9 “open” letter from forty-seven Republican Senators to Iran’s Supreme Leader warning him that he can’t count on the United States to follow through on any comprehensive nuclear deal makes it clear that many of them would like to blow such a deal up if given the chance.

Senate Democrats, including those who have co-sponsored the Corker bill, would be foolish to enable Republicans reckless enough to kill the best diplomatic opportunity to prevent a nuclear-armed Iran.

Given the high stakes, the first priority of all lawmakers should be to do no harm to the P5+1 effort, which is the result of years of diplomatic maneuvering and international pressure on Iran to constrain its nuclear program.

They should take a look at the fine print in S. 615 before they jump on board or rush it to a vote.

Majority Leader Mitch McConnell and Corker have already tried and failed to jam the bill through the Senate. Last week, they proposed bypassing the regular committee process and rushing the bill to the floor for a vote. This angered several Democrats, including Minority Leader Harry Reid, who called it “a transparently political move.”

Nevertheless, McConnell and Corker say they will bring up their bill before the end of March, by which time the nuclear negotiators from the P5+1 and Iran also hope to reach a political framework agreement. Republicans may also seek to attach legislation authored by Mark Kirk (R-Ill.) and Robert Menendez (D-N.J.) that would initiate additional sanctions on Iran.

The Corker bill has drawn the promise of a veto from the president—and for good reason.

The Corker bill would put on hold the implementation of the Iran nuclear deal for at least sixty-five days, and probably far more. This would delay key steps to constrain and reduce Iran's nuclear capabilities. The bill would also block the president's existing legislative authority to waive certain nuclear-related sanctions at the onset of an agreement, which by itself could wreck the deal.

A vote of disapproval on an Iran nuclear deal, even if a presidential veto of it were to be upheld, would severely undermine U.S. credibility and reduce the chance that Iran would continue to follow through on the agreement.

Corker claims the bill will require the president to regularly certify Iran is meeting its commitments under the nuclear agreement with the P5+1. In reality, the bill moves the goalposts by requiring the president to make certifications outside the scope or terms of what will likely be in the nuclear deal.

These additional conditions include: certifying that Iran is not providing support or financing for terrorism; that it has not delayed cooperation for “more than one week” with the International Atomic Energy Agency (IAEA); and has not engaged in centrifuge research that “may substantially enhance the enrichment capacity of Iran if deployed.” The bill says if he can’t make those certifications, Congress could reinstate all the sanctions previously waived or lifted under the agreement under expedited procedures.

Quite simply, the Corker bill would unnecessarily complicate, if not undermine, the strategy on Iran now being pursued by the United States and our UN Security Council partners, which is on the verge of producing an important breakthrough.

The P5+1 nuclear agreement with Iran that is taking shape would effectively block Iran’s major potential pathways to nuclear-weapons development—the uranium-enrichment route and the plutonium-separation route—and guard against a clandestine weapons program with enhanced IAEA inspections through the additional protocol and other measures. The deal would last some ten to fifteen years; the IAEA inspection authority would last indefinitely.

Contrary to Mr. Netanyahu’s assertions, and the unrealistic expectations of many Congressional lawmakers, there is no better deal on the horizon. Additional pressure (through still tougher sanctions) will not suddenly persuade Iran's leaders to completely dismantle their major nuclear facilities. For over a decade, Iran has resisted such an outcome. There is no reason to believe they would agree to do so now.

If Congress prematurely initiates new Iran-sanctions legislation, or takes action to delay, block or reject an effective P5+1 nuclear deal with Iran just days after it might be concluded, the United States would be blamed for spurning diplomacy, the chance for a diplomatic solution would greatly diminish, Iran could quickly expand its nuclear capacity, international support for the sanctions regime would weaken, and the risk of a military conflict and a nuclear-armed Iran would grow.

It is understandable that members of Congress want to play a role in foreign policy. And, in these highly partisan times, the temptation to second-guess the president’s Iran policy to score political points is strong. But some types of congressional action on this issue, at this time, can have far-reaching, negative ramifications.

Serious lawmakers have other, constructive options for weighing in. For example, a new bill introduced by Sen. Barbara Boxer (D-Calif.) proposes close monitoring of implementation of any P5+1 and Iran nuclear agreement and supports responding to potential noncompliance. If there is an agreement, the Congress should support additional U.S. funding to the IAEA to support its expanded monitoring mission in Iran.

Congress will, of course, have another critical role. It will eventually also need to take legislative action to permanently remove U.S. nuclear-related sanctions on Iran, but only when and if Iran takes the key steps called for under the comprehensive agreement to limit its nuclear capabilities and be more transparent about its current and past program.

If negotiators can close remaining gaps, the P5+1 agreement with Iran would be a major boost for U.S. and international security, for Israel and our other allies in the region, and for global efforts to prevent proliferation. Congress should be careful not to play the role of spoiler.

Daryl G. Kimball is Executive Director of the Arms Control Association.

Image: Flickr/U.S. Embassy Moldova/CC by-nc 2.0