The Washington Post | Amanda Erickson: Later this week, President Trump�is�expected to announce his decision to �decertify� the Iran nuclear deal, arguing that the arrangement isn't�in the best interests of the United States.�The world has been bracing for this decision since Trump won the election in November.�He has repeatedly derided the Iran accord as a stupid, loser deal, one of the worst he has ever seen.

But �decertifying� won't kill the accord automatically. It's much more complicated than that.�Here's what Trump may do this week and how it might play out domestically and internationally.

Why does Trump want to decertify the Iran deal?

By all accounts, Iran�has complied with the terms of the deal. U.S. officials have said so; European allies have agreed. The United Nations watchdog tasked with monitoring compliance has visited Iran several times and certified that the country is dismantling its nuclear program, per the terms of the deal. Last week, the U.S. defense secretary and the chairman of the Joint Chiefs of Staff expressed qualified support for the deal before Congress.

But the president and his administration say�Iran�is not following the�spirit�of the accord, which they see as�de facto noncompliance.�Secretary of State Rex Tillerson and others have said that Iran has not positively contributed to regional and international peace and security, an �expectation� embedded in the deal's preamble. They�noted that Iran still supports militant groups such as Hezbollah and Hamas and backs militias in Syria and Yemen. Iran has also continued to test ballistic missiles, something that irks the United States, even though such tests do not constitute a violation of the agreement.

What does �decertification� actually�mean?

The U.S. president is required by Congress to certify every 90 days that Iran is complying with the deal. Trump has done so twice; his next deadline is Oct. 15. Administration officials say�Trump will announce that he has decided to decertify the deal, arguing that it's not in the United States' national security interest to remain in the agreement.

On its own, that won't mean much. If the United States doesn't impose new sanctions, it's not technically in violation of its obligations under the agreement.�And The Washington Post has reported that Trump will hold off on recommending that Congress do so.

Interestingly, the administration could have chosen to kill the deal on its own, without Congress's help. Every 120 days, the administration issues waivers to keep old sanctions from being reimposed. Skip that step, and the administration could have�restarted�sanctions unilaterally come January. The president chose not to do that. My colleagues�have explained�the maneuver as �a middle ground of sorts between Trump, who has long wanted to withdraw from the agreement completely, and many congressional leaders and senior diplomatic, military and national security advisers, who say the deal is worth preserving with changes if possible.�

Could Congress decide to reimpose sanctions?

If Trump decertifies the deal, Congress will have 60 days to decide whether to reimpose sanctions on Iran, the ones that were suspended in exchange for that country's freeze on its nuclear weapons program.

That seems pretty unlikely.�Congress would need only 51 votes to impose those sanctions. But it doesn't seem as if Republicans have the support they need to push something through.�As The Post�reports, Senate Majority Leader Mitch McConnell (R-Ky.) does not want to add another contentious issue to the legislative calendar, especially not with midterm elections right around the corner.�Republican Sens. Jeff Flake (Ariz.), John McCain (Ariz.) and Susan Collins (Maine) have�also said they're not sure�how they would vote on sanctions. Sen. Rand Paul (R-Ky.)and House Foreign Affairs Committee Chairman Edward R. Royce (Calif.) say they don't think Trump should retreat from the deal. And Democrats seem universally opposed to new sanctions.

Given that, it's hard to imagine Republicans mustering the votes they need to impose any serious sanctions.

So, then, what is the president trying to accomplish?�

Even many proponents of decertification don't think the United States�needs to reimpose sanctions. They reckon that the Trump administration can use the process as a way of persuading European allies to join the United States in advocating for a stronger Iran deal.�In a speech at the Council on Foreign Relations last week, Sen. Tom Cotton (R-Ark.) laid out what that might look like. He�has called for a bill that would eliminate �sunset clauses� that lift restrictions on some Iranian nuclear activities after several years. He'd also like to see tougher inspections and new curbs on Iran's�ballistic and cruise missile programs.

Will European allies sign on?�

It's impossible to know for sure. But early indications suggest that if the�United States�backs out of the deal, it will do so�alone.

The other parties involved in the deal�and�the U.N. watchdog tasked with monitoring compliance say things are working.��We will not follow the United States in reneging on our international obligations with this deal,� a European Union�official told The Post on Thursday. Russian Foreign Minister Sergei Lavrov�told reporters, �It is very important to preserve it in its current form, and, of course, the participation of the United States will be a very significant factor in this regard.�

It's not totally clear how the international community will respond to Trump. But one thing is all but certain: If the United States backs out of the deal, it will isolate us from our allies and weaken our stature abroad.�As my colleagues�reported:
More than any other issue that has threatened transatlantic cohesion this year, President Trump�s decision to decertify Iranian compliance with the nuclear deal could start a chain of events that would sharply divide the United States from its closest traditional allies in the world.��After the Paris climate decision,� in which Trump withdrew the United States from a widely supported, painfully negotiated accord, �this could push multilateralism to the breaking point,� said a senior official from one of the three European signatories to the Iran deal.
How will the business community respond?

Since the deal was signed in 2015, several big companies have begun to do business in Iran. New sanctions by the United States would make things significantly more difficult.�As Vox explained:
New sanctions would also force American allies to choose between doing business with Iran or with the U.S. Iran has begun to reintegrate itself into the global economy in the past year, and it has developed meaningful business ties with big companies that are based in the countries that struck the Iran deal. For example, this summer Iran�signed a $5 billion agreement�with France�s Total SA and China�s state-run China National Petroleum Corporation to develop its South Pars natural gas field.
Already, the�E.U. has begun taking steps to protect its businesses from U.S. retaliation. Officials are looking at measures used in the 1990s to shield companies and individuals from secondary U.S. sanctions.��I've no doubt that if this scenario materializes, the European Union will act to protect the legitimate interests of our companies,��David O�Sullivan, the European Union�s ambassador to the United States, said at a September�meeting.

U.S. sanctions may even make it easier for European companies to compete in Iran. �U.S. decertification would not necessarily end the deal � the U.S. just wouldn't be part of it anymore,� Robert Litwak, a member of the National Security Council under President Bill Clinton and an expert on international security at the Woodrow Wilson Center,�told CNBC. �The Europeans won't return to sanctions so quickly. If this enables Airbus to beat out Boeing, they'd be delighted.�

How might Iran respond?

Iranian President Hassan Rouhani said last month that he will not reopen negotiations, and Iranian�Foreign Minister Mohammad Javad Zarif has said that his country would consider�walking away from the deal�if the United States�withdraws.�But Iran may stay in the agreement as long as the other signatories also stick to the deal.

As CNBC�put it:
If the U.S. decertifies the deal, �the ball immediately goes to Iran's court,� said Michael O'Hanlon, a foreign policy expert at the Brookings Institution. Iran �could have their cake and eat it too.�

It would be possible, O'Hanlon explained, for Iran to keep the benefits it gets from the agreement � namely, to continue to legally export�oil. Then, a few years down the road it could argue that the agreement is null due to a lack of compliance from the United States. It could then resume nuclear activities.

That's not an attractive prospect for U.S. decision-makers, because it would force them to make a choice: either attack Iran's nuclear facilities, or push for new sanctions from a group of countries that will almost certainly be reluctant to give up business ties with Iran.