The announcement last week of an agreement between Iran and the P5+1 on the parameters that would form the basis of a final nuclear agreement was a historic breakthrough. If the details outlined by the Obama administration hold, the final deal that is due to be negotiated by June 30, will have achieved the objective of creating conditions that will deter Iran from attempting a breakout – overt or covert – to a nuclear weapon. The concessions made by Iran at its known facilities will keep it at a breakout time of a year or longer for at least ten years, making it impossible for Iran to use those facilities to build a nuclear weapon without being quickly caught . And the inspections and verification regime that will last 25 years or longer will dramatically reduce Iran’s ability to covertly build a nuclear weapon.

However, the distance between parameters and a final agreement remains significant. Over the next three months the administration will have to deal with three major challenges as it attempts to finalize an agreement: (1) a skeptical U.S. Congress; (2) nervous Middle Eastern allies; and (3) the negotiations themselves.

A Concerned Congress

The first and most immediate challenge will be selling the agreement to Congress. Congressional leverage is found in the sanctions regime, which would have to be removed as part of any agreement. The president has the flexibility under current legislation to waive sanctions as Iran takes the necessary steps to limit its nuclear program. However, if Congress can pass legislation with a veto proof majority it can take away the president’s waiver authority or add new sanctions, thus undermining any deal.

The good news for the president is that members of Congress have indicated that in the aftermath of last week’s announcement, they do not plan to bring forward new sanctions legislation that could undermine negotiations. Instead, Congress will hold further sanctions in reserve in the event the negotiations collapse.

However, legislation introduced by Senator Bob Corker, Chairman of the Senate Foreign Relations Committee, may begin moving its way through the system when Congress returns next week. The legislation would give Congress 60 days in the aftermath of a deal to pass a resolution of disapproval that would take away the president’s ability to provide Iran with sanctions relief and thus kill any agreement. It would also restrict the president’s ability to provide any new relief during that 60-day review period. The president has promised to veto the legislation, but members may be able to put together a veto-proof majority.

The legislation is problematic in a number of ways. Most importantly, it needlessly jeopardizes ongoing negotiations. According to American negotiators, last month’s letter to the “Leaders of the Islamic Republic of Iran” written by Senator Tom Cotton and signed by 46 other Republican senators already soured the atmosphere in the negotiating room and made the negotiations more difficult. Inserting new legislation is an additional complicating variable in what is already likely to be a difficult environment . Iranian negotiators will express additional skepticism about American ability to implement the agreement and it might also lead the Iranian Parliament to retaliate with its own unhelpful legislation. If the final agreement with Iran is not to Congress’ liking it can, at any time, remove the president’s ability to provide sanctions relief and thus nullify the agreement. It does not have to do so before an agreement is even signed.

Another major problem with the legislation is that in order to continue to implement the agreement, the president would have to certify, in law, every 90 days that Iran has not supported or carried out a terrorist attack against any American person or target anywhere in the world. Any intelligence professional will tell you that this sets an impossible bar since the intelligence community is not omnipotent and does not know what it does not know. If there is a minor incident between Shia militias in Iraq and American forces would that nullify the nuclear agreement? It might, since as written the intelligence community would not be able to say with certainty if Iran was in anyway involved. Indeed, this language might inadvertently set up perverse incentives for hardliners in Tehran to support such terrorist actions in order to kill the deal.

In the end, the administration has a strong hand to play. Any deal-killing legislation will require a significant number of Democrats to join Republicans for a veto-proof majority, and given the surprising level of detail in last week’s announcement and the toughness of some of the provisions, it is hard to imagine so many members of the president’s own party ultimately opposing him. Even if Congress is insistent on passing legislation prior to June 30, the White House, with the support of Democratic proponents of legislation, will still have the flexibility to engage in negotiations that fix some of the most problematic language.

But the far wiser step for Congress would be to hold off until after June 30. At that point, it can play a useful role in judging any final agreement and pass legislation that includes tough oversight provisions to ensure that the executive branch effectively implements the agreement, and provides greater funding to make sure the necessary resources are available to implement an agreement in the most rigorous way possible.

Anxious Allies

Beyond Congress, the next difficult challenge for the Obama Administration will be managing the anxieties of our Middle Eastern partners – especially Saudi Arabia and Israel. In his statement announcing the agreement, the President clearly alluded to this concern and invited the Gulf Cooperation Council states to join him at a summit at Camp David to discuss mutual regional concerns.

The Saudis have publicly supported the agreement, though it is not clear how they view it privately. Their chief concern is not the nuclear agreement itself but a fear that this will lead to a pivot in American policy in the region, reorienting towards Iran and Shia actors more generally. They believe that the most direct threat from Iran comes from Iran’s support for Shia surrogates and proxies in Yemen, Syria, Lebanon, Iraq and elsewhere in the region.

Therefore, the most important reassurance that the United States can provide to its Gulf partners is not new hardware or a U.S. nuclear guarantee. Instead, it is a commitment to work together to counter Iranian asymmetric threats in the region. This entails a high level sustained strategic dialogue and coordinating mechanism between the United States and our partners on how to counter Iranian influence in the region. It can also include increased intelligence sharing, more aggressive interdictions of arms shipments, securing critical infrastructure, and working together to build partner capacity in the weak states that can counter Iranian proxies. Indeed, quiet U.S. support for the Saudi intervention in Yemen may be an initial indicator that the White House is moving in this direction.

Rather than focusing on the regional question, the Israelis are much more concerned with the nuclear agreement itself and the threat of a nuclear-armed Iran. Prime Minister Netanyahu came out publicly against the agreement, including in a series of television interviews on the Sunday talk shows. However, there also appears to be a shift in the Israeli approach as more voices, particularly in the security establishment, are arguing that Israel should work closely with the United States to improve the agreement instead of publicly opposing it.

There are a number of steps the United States can take to reassure the Israelis. First, through high-level dialogue it can offer reassurances to Israel about precisely how it plans to implement the agreement and how it will judge violations. This is crucial for the Israelis, whose greatest fear is that once a deal is struck the international community’s attention will turn elsewhere, and after a number of years of compliance Iran will be able to cheat with no consequences. The United States can also expand its already robust support for Israel’s ballistic missile defense systems and, similarly to the Gulf states, collaborate more closely on countering Iranian proxies and surrogates in the region.

Trying Talks

The third and final challenge may be the greatest, and that is negotiating the final agreement with Iran. This will not be easy. The same brinksmanship and hard negotiating tactics that characterized the last round will persist. There will be moments when all appears lost and that a deal may not be achievable.

Significant gaps remain. Most notably, there are still many details to be worked out on the schedule for the implementation of sanctions relief and what mechanism would need to be put in place to ensure that sanctions are “snapped back” into place if Iran violates the agreement. There is also concern about the precise details of the scope of research and development that Iran will be able to conduct under the agreement. And beyond this, it is also possible that Iran will backslide on some of the commitments it made in April.

However, with every major breakthrough it becomes more difficult for the parties to walk away. In particular, the agreement has been met with strong support from the Iranian people and expectations for sanctions relief are now sky high. Iran’s establishment has universally come out in support of the agreement including most recently the commander of Islamic Revolutionary Guards Corps, Mohammad Ali Jafari. It will be very difficult for Iran’s leaders to leave the field with nothing to show for the talks. It will also be easier to negotiate since most of the remaining details are more technical and less political, creating greater flexibility for technical experts to work out solutions. Thus, even though there are certain to be additional bumps in the road, the successful conclusion of a final comprehensive agreement is very likely.

In the end, the Obama administration is likely to face significant challenges from Congress, concerned partners, and in the negotiating room as it tries to complete this agreement. Furthermore, the challenges of implementation will be equally onerous. However, momentum is building and every step of the way it becomes increasingly likely that, against tough odds, the United States and Iran will achieve a historic breakthrough and resolve the challenges surrounding Iran’s nuclear program.

Ilan Goldenberg is a Senior Fellow and Director of the Middle East Security Program at the Center for a New American Security.