Should the Iran nuclear deal fall apart, the consequences for the Middle East region would be "unfathomable", according to a new report from the International Crisis Group.

The report, coming on the eve on Donald Trump's inauguration, urges the US president-elect to preserve and strengthen the landmark agreement, rather than tear it up as he has threatened to do.

Under the Joint Comprehensive Plan of Action (JCPOA), which took effect one year ago, Iran agreed to limit its uranium enrichment programme in return for sanctions relief - a pact derided by Trump as the "worst deal ever negotiated".

"Any attempt by the Trump administration to undercut the deal in the hope of 'fixing' it is likely to backfire ... Moreover, by destabilising the JCPOA, the new administration could usher in what it says it seeks to prevent: greater Iranian assertiveness, more regional instability and lower odds of resolving the conflicts in Syria, Iraq and Yemen - places where Iran is part of the problem and thus ought to be part of the solution," states the International Crisis Group's report, released on Monday.

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The report, which provides a status update on the first year of the JCPOA's implementation, notes that ongoing enmity between the United States and Iran has left the agreement vulnerable.

Since January 2016, the International Atomic Energy Agency has verified on six occasions that Iran was complying with its JCPOA obligations, the International Crisis Group found. But the report also acknowledges the bumpy road of implementation over the past year, including several minor technical violations by Iran, subsequently remedied, and problems with sanctions relief.

The relaxation of sanctions by the US, the European Union and the United Nations has allowed Iran to regain oil market share, with oil production and exports rebounding to pre-sanction levels of 3.85 million barrels a day. The country has also absorbed more than $11bn in foreign direct investment, the highest level in two decades - but Iran still lacks normal international banking ties, "hampering its reintegration into the global economy", the report notes.

The threat of sanctions "snapback", if the agreement falls apart, along with the possibility of new sanctions, continues to hang heavy amid concerns over Iran's regional ambitions and its ballistic missile tests.

"The agreement's collapse appears neither imminent nor inevitable. What seems more likely is its gradual erosion under the new US administration that could, deliberately or by neglect, undermine it," Ali Vaez, a senior Iran analyst with the International Crisis Group, told Al Jazeera.

Vaez noted that the deal's destabilisation could increase regional tensions and "push Iran to double down on policies it presents as essential to its national security, [such as] the ballistic missile programme ... and 'forward defence policy' of bolstering regional partners and proxies in Baghdad, Damascus and Beirut."

Despite Trump's bluster, the Iranian government has pointed out that the nuclear deal is non-negotiable and that no country would be allowed to affect its implementation.

To imagine a stronger pact can be built on its ruins is a chimera, as destroying it – even if gradually – would also destroy the hint of trust that led the parties to compromise. International Crisis Group report

The International Crisis Group's report, which suggests that the best path forward could be a mutually beneficial renegotiation of certain aspects of the deal, calls on Washington to give the treasury department more resources to roll back sanctions, while urging Iran to "stop using nuclear or regional brinkmanship as leverage". One option could be to strengthen some of the JCPOA's nuclear provisions in return for rolling back the US primary embargo, the report notes.

Other members of the P5+1 (the five permanent members of the UN Security Council plus Germany) should discourage Iran from overreacting to a possible change in US tone, "but also clearly tell Washington that if it unjustifiably walks away from the accord, it will do so alone," the report adds.

"[The deal's] unravelling now would have unfathomable consequences for the region, non-proliferation and multilateral diplomacy. To imagine a stronger pact can be built on its ruins is a chimera, as destroying it - even if gradually - would also destroy the hint of trust that led the parties to compromise," the report says.

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Massoumeh Torfeh, a research associate at the London School of Economics specialising in Iran, told Al Jazeera that while it remains unclear how Trump may proceed, his vow to quit the Trans-Pacific Partnership has highlighted his disdain for multilateral deals.

Although national security experts have asked Trump to walk back his hostility towards the Iran deal, he would have to be seen to be taking some action amid pressure from Israel, Torfeh noted: "So he would probably strike a new unilateral deal with Iran that would include carrots and sticks, extending the period in which Iran would not be allowed to enrich uranium. For that to be acceptable, the carrots would have to be substantial."

Failing that, Trump should steer clear of the deal entirely in the run-up to Iran's presidential election this spring, which will pose a test for the country's moderate government, she added.

"The hardliners in Iran would welcome any excuse to scrap the nuclear deal and, through that, undermine President Hassan Rouhani's chances for a second term," Torfeh said.

"They have already threatened that their plans for a return to nuclear enrichment are ready to be put to the parliament for approval."

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