Despite all the hostile posturing, it is unlikely that Trump’s administration will rip up the Iran deal.

With the appointment of retired General James “Mad Dog” Mattis as Donald Trumps’s secretary of defence, another staunch critic of Iran joins the next United States administration.

Lieutenant General Michael Flynn, Trump’s pick for national security adviser, and Mike Pompeo , his CIA director, have both taken a hard line on Iran. During the presidential campaign, Trump repeatedly bashed the nuclear deal, saying his “number one priority” would be to dismantle it. With a cabinet of anti-Iranian hawks, this could well happen.

Or maybe not.

The advantages of honouring the deal

Despite calling Iran the “single most enduring threat to stability and peace in the Middle East”, Mattis has defended the deal. In a recent speech, the retired Marine Corps general explained, “I don’t think that we can … take advantage of some new [president] – Republican or Democrat – and say, well, we’re not going to live up to our word on this agreement. I believe we would be alone if we did, and unilateral economic sanctions from us would not have anywhere near the impact of an allied approach to this.” ( PDF )

This view is shared by other Trump allies, like Senator Bob Corker, and with good reason. The Iran deal, known formally as the Joint Comprehensive Plan of Action (JCPOA), is a broad multilateral agreement involving the five permanent members of the United Nations Security Council and Germany (the so-called P5+1), along with the European Union.

While it would be possible, legally, for Trump to nullify the nuclear accord, doing so could isolate the US from the international community. Indeed, China and Iran have already urged Trump not to rescind the agreement. And killing the JCPOA would likely alienate Russia and jeopardise Trump’s plans to improve relations with Vladimir Putin.

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Other countries that are party to the deal may well refuse to re-impose sanctions, given they have already started trading with Iran.

The US already has its own unilateral sanctions against Iran, going back decades, which were just extended by Congress. The JCPOA did not lift those sanctions, and the US does not need to withdraw from the deal to maintain them.

Besides, the highly draconian measures in place before the agreement did not stop Iranian nuclear development. The Islamic Republic went from having 164 centrifuges in 2003 to 19,000 by the start of talks in 2013, despite comprehensive UN sanctions.

An American or Israeli military attack would likely only delay, not destroy, Iranian nuclear advances

Also, if the US pulled out of the agreement, Iran may use that as an excuse to withdraw, too, and start enriching uranium to much higher concentrations.

An American or Israeli military attack would likely only delay, not destroy, Iranian nuclear advances, as Mattis suggested.

Furthermore, both countries have allegedly attempted to disrupt Iran’s nuclear capabilities using highly sophisticated cyber warfare and sabotage, with only limited success.

Barack Obama’s nuclear accord is seemingly the only way to contain the Iranian programme. If Trump abandons it, he would likely struggle to prevent Iran from developing a nuclear weapon.

Impossible to renegotiate

Renegotiating (rather than killing) the deal would be difficult, too. The current agreement was the product of lengthy and intensive negotiations between multiple parties. It significantly curtailed Iran’s enrichment capabilities and lifted economic sanctions, allowing European and other companies to benefit.

Would the P5+1 really want to go through another tortuous series of negotiations to amend a deal that already gives them what they need? Moreover, the accord was controversial in Iran, and it is highly unlikely that a more punitive agreement would gain political acceptance there.

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Even the US’ Gulf allies, who are deeply suspicious of Iran, backed the deal in 2015 and may resist any attempts by Trump to change course.

As former Saudi intelligence chief Prince Turki al-Faisal said at an event recently, “I don’t think he should scrap it. It’s been worked on for many years and the general consensus in the world, not just the United States, is that it has achieved an objective, which is a 15-year hiatus in the programme”.

Although Israel’s Prime Minister Benjamin Netanyahu strongly opposed the agreement, military chief Lieutenant-General Gadi Eisenkot and other members of the Israeli security establishment have expressed their support .

A possible confrontation

So, it seems likely that the deal will remain in place. But that doesn’t mean Trump’s administration will cosy up to Iran. Far from it.

Mattis is deeply hostile to the Islamic Republic, and apparently lost his job as US CENTCOM commander under President Obama due to his extreme attitudes.

In the speech cited above, he even implied that Iran was colluding with the Islamic State of Iraq and the Levant, despite the fact that Iranian forces are fighting the group in Iraq.

This is painfully reminiscent of George W Bush’s allegations about al-Qaeda and Saddam Hussein. Indeed, Politico has reported that some in the Pentagon fear Mattis’ excessive antipathy to Iran could result in confrontation.

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Then there is Michael Flynn, who described the threat posed by Iran in almost apocalyptic terms during congressional testimony last year (PDF). As head of the Defense Intelligence Agency, he reportedly believed that Iran had a role in the attack on the US consulate in Benghazi, and insisted analysts find evidence to prove his convictions (there is no evidence of Iranian involvement).

The parallels with the intelligence failure leading up to the 2003 Iraq War do not need to be spelt out. According to former CIA analyst Paul Pillar, writing in the National Interest, “Ingredients are falling, tragically, into place for a possible war with Iran”.

So, while it is unlikely Trump will torpedo the nuclear deal, his administration may still pick a fight with the Islamic Republic. That is something we should all fear.

Rupert Stone is an independent journalist working on national security and counterterrorism.

The views expressed in this article are the author’s own and do not necessarily reflect Al Jazeera’s editorial policy.