Announcing the nuclear deal agreed this week between the Islamic Republic of Iran and the so-called E3+3 (the EU3 of France, Germany and the United Kingdom plus the United States, Russia, and China), US President Barack Obama declared: 'This deal is not built on trust, it is built on verification.'

The same rhetorical defence had been invoked by Obama and his Secretary of State, John Kerry, in November 2013, when the two sides had first reached agreement on a Joint Plan of Action (JPOA), now subsumed within the final comprehensive JPOA. Despite Obama's public dismissal of the role played by trust, it is our contention that the top US negotiators would not have signed this deal had there not been trust in their Iranian counterparts.

Obama's repeated statements over the past 48 hours that trust played no part in this deal is not in itself an indication that trust was absent. It is an irony of trust that a concept so valued in interpersonal relations is seen by leaders – especially when dealing with adversaries – as being toxic to international relations. This is because they worry that appeals to trust will be seen as a naive and ineffectual basis on which to formulate national security policy. Although the deal has been hailed in many quarters as a great success, it faces a serious challenge from those members of Congress who see it as betraying US interests and selling out America's friend, Israel. Faced with the hard task of legitimating the Iran deal to a suspicious and hard-line US political elite, it is not surprising that Obama has eschewed the 'soft' language of trust in favour of the 'hard' technical promise of a verification regime that is unprecedented in nuclear diplomacy.

We reject the dichotomous framing of trust and verification implicit in Obama's statement. There is no level of verification that can stop a determined proliferator with the technological capability to make nuclear weapons. This is why opponents of the deal who believe Iran is hell-bent on acquiring nuclear weapons are not satisfied that any level of inspections can provide assurances that Iran’s nuclear programme is only for peaceful purposes. Consequently, even with the most robust verification machinery in place, there still has to be some level of trust at the highest levels of the US government in the sincerity and integrity of those negotiating on behalf of Iran.

The strong personal chemistry between Kerry and his Iranian counterpart, Javid Zarif, should not be underestimated in any explanation of how the Iran deal became possible. Their frequent face-to-face interactions, including the last two weeks spent together finalising the deal in Vienna, appear to have fostered mutual respect, growing empathy, and trust in each other’s bona fides. This assessment is a provisional one in the absence of detailed empirical evidence that we expect to emerge in the months and years to follow, but it also accords with recent work in international relations that has identified a key role for face-to-face interactions in helping decision makers to assess the sincerity of others.

Obama has relied heavily on Kerry to deliver the jewel in the crown of his foreign policy legacy, and without his trust in Kerry, it is hard to imagine that the Iran nuclear deal would have taken the shape it did. A historical parallel here would be the trust that Ronald Reagan placed in his Secretary of State, George Shultz, when they were negotiating with the Soviet Union at the end of the Cold War.

There is a further dimension of trust involved in the Vienna agreement. This concerns the question of whether Obama and Kerry are right to trust that President Rouhani and Zarif will retain the political capacity to follow through on the implementation of the deal in the face of Iranian elements that might actively oppose it. The Obama administration might reply that the so-called 'snap-back' provisions in the agreement, under which sanctions would be reimposed in the event of Iranian non-compliance, are a safeguard against this eventuality.

But this response does not obviate the fact that US decision makers are trusting in the authority of Rouhani and Zarif. The Boston Globe reported that in a particularly heated exchange during the endgame in Vienna, Kerry demanded to know from Zarif: 'Do you have the authority to negotiate this deal and bring it to closure?' Zarif reportedly confirmed that he did. The authority question, and the issue of trust that resides in it, bears crucially on how far the lead Iranian negotiators retain the confidence – and indeed the trust – of Iran’s chief nuclear decision maker, the Supreme Leader, Ayatollah Ali Khamenei. In previous negotiations, it has been the Supreme Leader who has pulled the plug on any prospective agreement (eg, the 2009 fuel swap proposal), and retaining his support is crucial to the implementation of the agreement.

Despite our suggestion that Kerry and Zarif have developed a relationship of interpersonal trust and that this was an important factor in securing the deal in July 2015, we recognise that there is a continuing trust deficit at the interstate level. Indeed, Obama's appeal to verification and not trust is indicative of how far the two countries are locked into cultures of distrust. This distrust is institutionalised within structures of government in both countries and is deeply embedded in societal narratives. While interpersonal trust may have facilitated the present agreement, its successful implementation will depend upon how far the habits and practices of trusting become institutionalised.

Joshua Baker
Doctoral Researcher, Institute for Conflict, Cooperation and Security and Department of Political Science and International Studies, University of Birmingham

Professor Nicholas J. Wheeler
Professor of International Relations and Director of the Institute for Conflict, Cooperation and Security, University of Birmingham