Trump has called the Iran deal ‘the worst deal ever’ [Michael Conroy/AP Photo]

If Trump refuses to certify, the issue goes to Congress.

Legislators will have a non-binding 60 day period to debate the deal.

Congress can decide to introduce or restore sanctions.

It remains to be seen whether that will happen as several prominent Republicans are undecided on the issue or do not want the deal to unravel.

Would Trump be violating the nuclear deal?

Not certifying the deal would not be a violation of JCPOA in itself. However, it does pave the way for Congress to introduce new sanctions, which could be in breach of US commitments under the agreement.

The onus on breaching the deal would, therefore, be with US legislators.

Would it be easy to introduce new sanctions?

While opposition to the Iran deal as it stands is strong, any attempt to scrap it would face resistance from members of the minority Democratic Party, as well as some Republicans, such as Senator Lindsay Graham, who has called on Trump to renegotiate parts of the agreement instead of scrapping it entirely.

How has Iran reacted?

Foreign Minister Zarif has threatened to partially or fully withdraw from the deal in the event of new US sanctions on Tehran.

Analysts say hardliners in Iran will be empowered by any US violation of the deal and would use it as an opportunity to block any further rapprochement with Washington.

“If anything Iran has gone out of its way to show it is compliant with the nuclear deal but what it will do is put pressure on the European countries to stand up for the deal for them to keep up with their part of the bargain,” Durham University’s Professor Anoush Ehteshami told Al Jazeera.

Iran reduced its enriched uranium stockpiles and centrifuges as part of the deal [Mehr News Agency/AP Photo]

How have US allies reacted?

European leaders have taken the unusual step of publicly calling on the US to abide by the deal and have affirmed that Iran is upholding its commitments under JCPOA.

On Friday, the British embassy in Washington, DC, took the unusual step of posting an animation on Twitter showing how Iran was complying with the deal.

French President Emmanuel Macron has told the US that not honouring its side of the deal could push Iran into producing a nuclear weapon in the future.

European states have enjoyed burgeoning trade ties with Iran since the deal came into force and experts say US breaches of the deal would damage its reputation as a reliable partner.

“Europe and the rest of the world would perceive the US as an international troublemaker and unreliable partner,” Arshin Adib-Moghaddam of the School of African and Oriental Studies said.

What other sanctions has the US placed on Iran?

As recently as last July, the US imposed sanctions on 18 Iranian individuals and entities for supporting what it said was “transnational criminal activity”.

Sanctions related to Iran’s ballistic missile programme, its activities in other countries and its alleged ties to proscribed groups remain unaffected by JCPOA.