What will Trump do about the Iran nuclear deal? - BBC News
Will it kill the deal if Trump refuses to recertify it, and how might Iran respond?
All the indications are that President Trump will refuse to recertify the present Iran nuclear deal some time before the due date of 15 October. This would light a fuse that could potentially explode the agreement. It raises questions about how Iran will respond. And it creates huge diplomatic difficulties between the US and many of its key European allies who wholeheartedly back the deal.

The agreement, negotiated with Iran by the five permanent members of the UN Security Council together with Germany and the European Union, was reached in July 2015. Its aim was to ensure that Iran's nuclear programme was entirely peaceful.

The deal, known as the Joint Comprehensive Plan of Action (JCPOA), began to be implemented in January 2016. In return for the progressive lifting of a range of economic sanctions, Iran halted some of its activities and reduced others within strict limits, all open to verification by international inspectors.

There are four crucial things to remember about the deal.

Forcing Iran to halt its nuclear activities altogether was not feasible. Many of the restrictions imposed by the JCPOA contain "sunset clauses", which run out after a number of years. What happens then is a valid question, but it was felt by all the parties that constraining Iran's nuclear programme for the immediate future was a deal worth taking.

It is easy to forget that there was a real concern at the time the deal was being negotiated that without an agreement there could be a military conflict.

Donald Trump spoke at rallies criticising the Iran nuclear deal, during the presidential campaign

Israel was pressing for military action. Many of Iran's Arab enemies in the Gulf quietly backed such a step and there were questions as to whether the US itself might have to use force to prevent Iran developing the capability to manufacture and deliver a nuclear weapon.

Sound familiar? It is much like the position that the US is in today with North Korea. The JCPOA was intended to manage Iran's nuclear activities, avoiding a recourse to war.

The JCPOA was about Iran's nuclear programme and nothing else. Iran does many things that the US, and its European and Middle Eastern allies, believe are damaging to security in the region.

That is an important but a different matter, one that I will come back to in a moment. The JCPOA was and is a nuclear deal, pure and simple.

And that brings me to perhaps the most fundamental point of all.

Everyone - and that includes the UN's nuclear watchdog and all of the signatories (including senior figures in the Trump administration) - believes that Iran is abiding by the agreement to the letter.

This video can not be played To play this video you need to enable JavaScript in your browser. A timeline of what Trump's said about the Iran deal

It wanted to have some oversight over the application of the JCPOA and brought in legislation, the Iran Nuclear Agreement Review Act (INARA), which requires the US president to certify every 90 days not just that Iran is complying with the deal, but that the continued suspension of nuclear-related US economic sanctions remains vital to the national security interests of the United States.

So far - despite criticising the Iran nuclear deal at every opportunity - President Trump has grudgingly recertified the JCPOA under this legislation. But now he looks set to change his mind.

Assuming he does now refuse to recertify the deal, insisting that it is no longer in US interests to do so, what then? What does it mean? And what happens next?

The crucial point to grasp is that the Iran deal (JCPOA) and the US legislation (INARA) are two totally different things.

By decertifying the Iran deal, Mr Trump would not be withdrawing from it. He would certainly be making a fundamental point about his view of its utility. He would be opening up a path under which Congress could effectively cease US compliance with the deal.

But in practical terms, this is a multinational agreement that is being adhered to and thus it would remain active with or without a certification from Mr Trump.

Of course, having decertified the deal, the president could simply reimpose some or all of the economic sanctions that have been waived under the JCPOA, and this would certainly mean that the US was no longer complying with its terms of the deal.

But the more likely scenario would be that - under the US INARA legislation - the whole issue would go to Capitol Hill for the US Congress to decide.

Opinion there is divided. There is clearly no warmth felt towards Tehran, but at this stage it is not clear what Congress might do.

The Iran nuclear deal was announced in Vienna, Austria, in July 2015

Would it reimpose some or all sanctions - thus pulling the US out of the deal - or decide to bide its time? There are indications that some of those on Capitol Hill most critical of the deal at the time are now reluctant to tear it up.

Now we come to another crucial aspect of this whole business: the ostensible reason why Mr Trump may decertify the agreement in the first place.

Iran is seen by the West and its allies as a major problem in the region. Paradoxically, the US itself helped to facilitate Iran's rise as a regional player through its destruction of the Saddam Hussein government in Iraq.

Iran has an important say with the Shia-dominated government in Baghdad. It - along with its proxy militias - is a major player in Syria. And it has a hand in the conflict in Yemen, though there is debate about the scale of its activities there.

Add in worries about its missile programmes and its alleged support for terrorism, and there are good reasons for concern about its growing regional influence.

The JCPOA agreement has not changed Iran's wider behaviour.

Under the deal, Iran's uranium stockpile will be reduced by 98% to 300kg (0.3 tonnes) for 15 years

The activities of Iran's Revolutionary Guard Corps and its missile-research effort have continued.

The JCPOA was never intended to tackle these wider issues. But in some basic sense, Mr Trump looks set to contend that Iran is not living up to the "spirit" of the deal - it's not playing nice - and that is why he will choose to decertify it.

The Trump administration wants to get tough with Tehran.

The president is likely to set his decertification of the JCPOA as part of a wider set of policies intended to punish Iran, as he would see it, for its bad behaviour.

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All sorts of new sanctions could be on the table. Remember, there is still a whole battery of sanctions in place both from the US and the EU for a variety of other things - separate from the nuclear programme - such as terrorism or human rights violations.

One suggestion is that the Trump administration might decide to brand the whole of Iran's Revolutionary Guard Corps as a terrorist entity.

This body - part security force, part military, part ideological vanguard - also controls a significant part of the Iranian economy. More sanctions here could cause problems not just for Iran, but between the US and those of its allies who want to open up trade with Tehran.

So if, as expected, Mr Trump does decertify the Iran nuclear deal, it is not necessarily the end of the agreement.

Iranian President Hassan Rouhani said the US would damage its own reputation if it violates the nuclear deal

America's allies are lining up to encourage both the White House and Congress to stick with the deal.

Even if Congress chooses not to reapply sanctions for now, the next problem becomes the scope and impact of the Trump administration's wider policy towards Tehran.

Iran for now is likely to do nothing. It will see decertification as an internal legal US matter, and is likely to continue to adhere to the agreement. Indeed, it may well relish the widening split between Washington and its key European allies.

But the way Tehran responds to any other US steps may well decide the fate of the nuclear deal.

Remember, this is a US administration dominated by military figures, many of whom have been up against Iranian-backed forces in the field.

They may back the nuclear deal, but also want to see Tehran held to account for its actions.

Insulating the JCPOA from team Trump's wider Iran policy is not going to be easy, and over time, it may well influence thinking towards the utility of the agreement in Iran itself.