Now that Trump has pulled the US out, the Iran nuclear deal will eventually collapse – here’s why

As the benefits disappear it will become harder and harder for the Iranian government to rationalise continued adherence to the agreement

After months of hints Donald Trump has finally acted to kill the 2015 nuclear agreement known as the Joint Comprehensive Plan of Action (JCPOA). In the short term, however, the effects of his announcement will be limited. The Iranian government has condemned the decision but President Rouhani also declared that Iran will continue to adhere to the agreement as long as the other parties to it if the P5 +1 (the non-American members of the UN Security Council and Germany) continue to do so.

The latter, for their part, have asserted their continued commitment to the JCPOA. For the Iranians sticking to the deal for now is a logical course to take in order to ensure that it is Trump, and not them, who is the focus of international recriminations. For the Europeans the insistence that the deal remains alive generates space to try and come up with a plan to salvage something from it.

The JCPOA, nevertheless, is now on life support and its eventual demise is likely. Once US sanctions are restored they will gradually undermine the rationale for Iran to continue to adhere to the deal. The threat of US sanctions on anyone who continues to do business with Iran is already leading to a degree of economic disengagement, negating the economic benefits which were the primary incentive for Iran to sign the deal. As those benefits disappear it will become harder and harder for the Iranian government to rationalise continued adherence to the agreement.

The only way that the deal may survive is if the Europeans can somehow ensure that Iran continues to see sufficient economic benefits from the JCPOA to enable Rouhani to justify remaining in the deal. That, however, would require a robust EU response to Trump, including the passage of legislation shielding European firms from US secondary sanctions and the threat of retaliatory action against US economic interests. It is hard, however, to see the EU risking a trade war with the USA over Iran, and even if they do act, it may still not be enough to prevent European firms from deciding that continuing to do business in Iran is too risky.

While the eventual collapse of the nuclear deal is thus highly likely, what happens after that is harder to predict. To some extent it will depend on Iranian politics. Rouhani does not want a conflict with the US and will actively seek ways of avoiding one, but Trump's declaration discredits him and strengthens the position of those in Tehran most hostile to the US. The arguments of Iranian hardliners – that the “Great Satan” can never be trusted and that it is bent on the destruction of the Islamic regime – are seemingly confirmed by Trump's actions. A shift in the balance of political power back toward Iranian conservatives is thus a probable outcome in the medium term.

With hardliners back in power, Iran could be expected to restore its nuclear programme to a similar scale to that which existed before 2015 (even if it does not renew weapons-related aspects of that programme) and to pursue its efforts to expand its regional influence with ever greater vigour. The Saudis and the Israelis, buoyed by Trump's implicit (or explicit) support will push back hard, leading to an escalation of proxy conflicts in Yemen and Syria and an increasing risk of direct conflict between the main protagonists themselves.

In Trump's mind, of course, this is not how events will play out. His claim is that the Iranian regime was on the point of total capitulation in 2015 only for Obama to “throw it a lifeline” in the form of the nuclear deal. According to this logic, the restoration of sanctions will bring Tehran to its knees and force it to comply with all of Trump's demands.

There is little reason, however, to take this scenario seriously. In the first place, sanctions had not brought Iran “to its knees” by 2015. Its negotiators remained as insistent on retaining the right to enrich uranium as they had for the previous decade. Had Obama not conceded that right there would have been no deal. Moreover, there is no chance that the sanctions regime that Trump is attempting to restore will be as effective as that in place under Obama. The Europeans will likely cooperate in a half-hearted fashion but China and Russia will not and nor will many other consumers of Iran's oil.

Trump is thus seeking to get a tougher deal than Obama managed with less leverage, with predictable results. If and when the nuclear deal collapses Iran will restore its nuclear programme and renewed US sanctions will fail to deter it from doing so. Regional tensions with rise. Iran will increase its stockpile of enriched uranium, and this will put pressure on the US government, from both Israel and its own supporters, to “do something” to stop it.

Trump's decision, in short, will do nothing to resolve the Iranian nuclear issue while making war in the Middle East considerably more likely.

Dr Steven Hurst is a reader in politics at Manchester Metropolitan University