Iran needs to get off the fence and decide if it will make the compromises necessary to clinch an agreement.

Now that the Corker-Cardin legislation has been adopted without poison pills attached, it is virtually certain that Congress will be unable to block President Obama’s ability to conclude and begin implementing a nuclear agreement with Iran that he believes meets U.S. requirements. The main domestic impediment to a deal lies in Iran. If negotiations are to be brought to a successful conclusion, Supreme Leader Khamenei must decide that he wants an agreement, that he is willing to make the hard choices necessary to achieve one, and that he is prepared to use his authority to bring Iranian critics on board.

The Corker-Cardin bill, which was eventually embraced and signed into law by the President, establishes a process for Congress to review, vote on, and potentially reject an Iran nuclear agreement. A joint resolution of disapproval would prevent the Obama Administration from suspending statutory U.S. sanctions and therefore from implementing the agreement. However, many members of Congress regarded the bill not as a referendum on the emerging nuclear deal but as a vehicle for giving them a say on a highly consequential American international undertaking. If and when an agreement is sent to Congress, a sizable number are likely to support it as the most promising means of resolving the Iran nuclear issue peacefully.

Moreover, a joint resolution of disapproval can be vetoed by the President. Consequently, to scuttle the deal, opponents would need a two-thirds majority in both houses of Congress to override a presidential veto. With the May 7 letter to the President from 151 House Democrats supporting the Iran nuclear negotiations, it appears Obama will have the one-third in the House needed to sustain his veto. If the final agreement preserves and successfully builds on the political framework reached by the P5+1 countries and Iran in Lausanne on April 2, the administration should also be able to garner the support of at least the 34 Members required to prevent a veto override in the Senate.

Senator Ted Cruz, a strong opponent of the emerging nuclear deal, conceded as much. Referring to the Corker bill, he said “it is a virtual certainty that, no matter how terrible this deal is, it will go into effect and this legislation is unlikely to stop it.”

The Lausanne Framework: A Promising Foundation

Actually, the emerging nuclear deal is not terrible at all. The Lausanne framework indicates that the Obama administration is well on its way to achieving its main negotiating objectives:

· A combination of constraints—including reductions from more than 9,000 to just over 5,000 centrifuges enriching uranium, from over 19,000 to around 6,000 installed centrifuges, and from around 10,000 kilograms to 300 kilograms of enriched uranium—will increase the time it would take Iran to produce enough fissile material for a single nuclear weapon to at least one year for a period of at least ten years.

· The re-design of the Arak heavy water reactor, the requirement to send its spent fuel out of Iran, and the ban on reprocessing facilities will effectively block the plutonium path to a nuclear weapon.

· Far-reaching verification arrangements—including adherence to the IAEA Additional Protocol, continuous surveillance of key elements of the uranium and centrifuge supply chain, and a monitored procurement channel—will provide confidence in the ability to deter and detect covert Iranian activities.

What is publicly known about the Lausanne framework comes mainly from a U.S.-issued fact sheet as well as from a European Union-Iranian joint statement that was short on details at Iran’s insistence. Although the Iranians have complained that the U.S. fact sheet is highly selective and one-sided in featuring those elements of the framework most favorable to the United States, the Americans assert that Iran agreed to everything in the fact sheet—and Iranian negotiators do not dispute that claim.

Indeed, as hinted at in the fact sheet, more has been agreed than has been made public. For example:

· The fact sheet states that “Iran will engage in limited research and development with its advanced centrifuges, according to a schedule and parameters which have been agreed to by the P5+1.” Such constraints would prevent Iran from gaining full confidence in the performance of advanced centrifuges during the agreement’s initial ten years, requiring Iran to carry out additional research and development after ten years and delaying the operational deployment of the more efficient machines.

· The fact sheet also states that “beyond ten years, Iran will abide by its enrichment and enrichment research and development plan submitted to the IAEA.” All parties to the Additional Protocol are obliged to submit such a plan. While Tehran’s plan will be based on Iran’s own evolving capabilities and perceived needs and will not be formally agreed with the P5+1, it appears that there may already be a mutual understanding of its key elements that will provide assurance that, when certain restrictions on Iran’s enrichment program expire after ten years, Iran’s enrichment capacity will only grow at a measured and predictable pace.

· The “disputes resolution process” mentioned in the fact sheet also seems to have been agreed but not yet made public. A workable mechanism—one that could ensure that one or a couple of parties could not, for example, block an inspection—would build confidence that the agreement will be faithfully implemented.

The Lausanne framework left a large number of important issues unresolved. But its publicly and privately agreed elements provided a promising foundation for working out a detailed comprehensive agreement in succeeding months.

Iranian Public Statements: A Complicating Factor

The momentum achieved in the final days in Lausanne, however, has not been sustained. Despite frequent meetings at the ministerial, political directors, and experts levels—both between Iran and the United States and Iran and the P5+1—insufficient progress has been made since April 2, and only about three weeks remain before the June 30 target date, when the current interim agreement will expire.

A serious complicating factor—aside from the usual hard bargaining that can be expected in any high-stakes negotiating endgame—has been a series of public statements by Supreme Leader Khamenei and other senior Iranians that have seemed to contradict and backtrack from solutions already worked out in the negotiations.

Within a week of the Lausanne agreement, the Supreme Leader asserted that all sanctions must be removed as soon as a final agreement is reached. But the notion of immediate removal of sanctions is at variance with Iran’s earlier acceptance of the idea, as recorded in the EU-Iran joint statement, that relief from U.S. and EU sanctions would only come “simultaneously with the IAEA-verified implementation by Iran of its key nuclear commitments.” As agreed at Lausanne, what Iran would need to do to trigger sanctions relief would include such significant undertakings as removing excess centrifuges to monitored storage, removing a critical component of the Arak reactor, reducing enriched uranium stocks to 300 kilograms, repurposing the Fordow enrichment facility, and taking agreed steps to address concerns about past Iranian activities believed to be related to nuclear weapons development.

Iranian negotiators are therefore faced with the challenge of reconciling what they have already agreed to with the statements of their Supreme Leader and the expectations those statements have created within Iran for the premature removal of sanctions. One way they have tried to square the circle is to admit that sanctions relief would follow Iranian implementation of key nuclear commitments but contend that those commitments can be implemented in an impossibly short period of time—a matter of weeks rather than the half year or more that would almost surely be required. Continued Iranian insistence on the position that all sanctions must “cease to apply” (their preferred formulation) as soon as the comprehensive agreement is reached or in an unrealistically short period of time thereafter would undoubtedly ensure deadlock.

Khamenei has also been publicly adamant that IAEA inspectors will not be granted access to Iranian military installations. But Iranian negotiators freely acknowledge that the Additional Protocol to which Iran is committed permits IAEA access to any location where questions of compliance have arisen, civilian or military. To square this circle, Iran’s negotiators say that “managed access” procedures—which are provided for in the Additional Protocol to protect parties’ legitimate secrets unrelated to their nuclear nonproliferation obligations—can be used at Iran’s military installations to protect its national security, thereby not crossing the Leader’s redline.

However, the notional managed access procedure described by Deputy Foreign Minister Abbas Araghchi in a May 25 television interview is so excessively constrained as to be comical. In the example provided by Araghchi, an IAEA inspector is blindfolded and taken into an installation where everything is covered up so that nothing can be seen. The blindfold is removed, the inspector is allowed to take an environmental sample with a handkerchief, and the inspector is then blindfolded again and escorted out of the installation. The IAEA would clearly regard such a procedure as woefully inadequate to meet its verification responsibilities.

It is unclear why the Supreme Leader is taking public positions that appear to contradict agreements reached by his negotiators. One explanation is that Iran’s negotiating team has gotten out ahead of the Leader’s instructions. But it is highly unlikely that Iranian negotiators are operating outside his guidance. Especially on issues as politically sensitive as the timing of sanctions relief and access to military installations, the Iranian negotiating team would want to be confident of the Leader’s support before committing to solutions.

Another possible explanation is that the apparent discrepancies between the Leader’s public comments and solutions already reached are part of a coordinated negotiating strategy in which the Iranians first re-open areas of agreement and then eventually return to the original agreements in exchange for P5+1 concessions on remaining unresolved issues.

It is also possible that Khamenei calculates that a tough public stance is temporarily necessary to placate Iranian critics of the deal but is ultimately prepared to stand by the concessions that will be required to conclude an agreement.

And of course, it is also possible that, confronted by strong domestic criticism of the Lausanne framework, the Supreme Leader has decided to walk back earlier concessions and re-draw his redlines. Whatever the explanation or combination of explanations, the public pronouncements coming from Tehran do not augur well for the negotiations. To get a deal, Iranian negotiators will have to re-commit to everything they have already accepted, even if doing so seems inconsistent with public expectations generated by the Leader’s statements. To compensate, Iran’s negotiators may feel compelled to take rigid positions on some of the critical issues left unresolved in the Lausanne framework.

Difficult Issues Remain

Perhaps the most difficult unresolved issue involves the question of past Iranian activities believed to be related to the development of nuclear weapons. The P5+1 have proposed a list of steps Iran would need to take to address international concerns about those activities. An important component on that list is a series of interviews by the IAEA of Iranian scientists and other individuals believed to have participated in the suspect activities. But the Supreme Leader has staked out an uncompromising public position that Iran’s nuclear scientists cannot be interviewed by the IAEA. Continuing to hold key participants in those activities off-limits to the IAEA can only reinforce the impasse on one of the most important issues remaining in the negotiations. Iranian officials claim that there are other means of resolving the question of past nuclear activities, but such means have not been identified, at least not publicly.

In addition to tackling the major outstanding issues, the negotiators also need to agree on a huge number of technical details required to implement the agreement. The P5+1 have proposed three lengthy technical annexes to the basic political agreement. The Iranians have tended to resist highly detailed annexes, maintaining that the necessary details can be worked out in the course of implementation. But the P5+1, especially the United States, insist that details need to be nailed down now to avoid implementation problems later.

Take More Time if Necessary

Given the significant issues still unresolved as well as the crucial technical details still to be agreed, it is very hard to imagine that a satisfactory comprehensive agreement can be achieved by the June 30 expiration of the Joint Plan of Action, the current interim agreement. Indeed, Iran may be counting on the fast-approaching June 30 terminal date to put pressure on the United States to make concessions on unresolved issues and settle for less detailed technical annexes.

There are arguments for getting the job done by the end of this month. Critics might claim that any extension would enable Iran to “play for time,” and support for imposing new legislative sanctions could be revived. Advocates of an agreement might assert that another extension would risk allowing the current opportunity for an agreement to slip away.

But meeting U.S. requirements for a sound agreement is clearly more important than meeting a self-imposed deadline. Even Congressional skeptics of the negotiations would presumably prefer to take the additional time needed to achieve an effective agreement rather than be pressured to make unwarranted concessions under artificial time pressure.

Indeed, it is Iran, not the United States, that should feel pressure to finish this month. It is Iran that continues to suffer under sanctions and the Iranian people who are impatient for economic recovery and an end to their pariah status. And it is Iran whose nuclear program remains frozen in virtually all consequential respects. The United States can well afford to take the additional several weeks, or even several months, to ensure that its requirements are met.

With U.S. Resolve, the Choice Will Be Iran's

The negotiators have come close to agreement. But a final deal could still prove elusive. Perhaps the biggest risk of failure is an Iranian miscalculation that the Obama administration is so committed to an agreement, and so eager for one, that it is prepared to conclude the negotiations largely on Iran’s terms. President Obama clearly wants an agreement, but he and his administration have a definite idea of the kind of agreement they can support. They need to make clear that, if Iran cannot accept such an agreement, they are prepared to walk away.

The choice will then be up to Iran, especially to the Supreme Leader. He will finally have to get off the fence and authorize his negotiators to accept the solutions necessary to conclude the deal (including some he has recently and strongly criticized). He can no longer have it both ways, giving general, rhetorical support to his negotiators but publicly articulating redlines that make their job difficult. Unless he throws his weight clearly behind an agreement, the best opportunity for a peaceful solution to the Iran nuclear issue will be missed.

Robert Einhorn is a senior fellow at the Brookings Institution. From 2009 to 2013, while serving as the State Department’s Special Advisor for Nonproliferation and Arms Control, he was a senior member of the U.S. delegation to the Iran nuclear negotiations.