Why does cooperation work or fail? The case of EU-US sanction policy against Iran

In the article, we explore the factors which brought about the transatlantic coordination of the policy of imposing sanctions on Iran. We will mainly focus on the events in the 21st century when the new incentives for cooperation appeared due to the growing concern over the development of Iran’s nuclear programme. Considering the capabilities of using the tools of economic statecraft and diplomacy, we claim that the EU-US cooperation can be termed a co-leadership. The assessment and the reasons for the transatlantic break-up on this matter during the presidency of Donald Trump was examined using the concept of relative gains. We evaluate to what extent the initial goals were achieved in practice, and we also try to predict the possible consequences of the US withdrawal from the Joint Comprehensive Plan of Action (JCPOA). As to whether the effectiveness of the sanctions through the cooperation has been enhanced, the answer is ambivalent. On the one hand, the cooperating transatlantic partners managed to coerce Iran through isolating the country from international economic contacts and negotiated the JCPOA. On the other hand, Trump’s renouncement of this agreement brought many negative consequences and undermined the earlier joint effort