The U.S. decision to withdraw from the Joint Comprehensive Plan of Action (JCPOA), the agreement that capped Iranian nuclear ambitions in exchange for its reintegration into the global economy, has yet to take its toll. Given the relative weakness of U.S.-Iran economic ties, the deal — and subsequent rejection by the United States — would never have a profound impact on trade between those countries. Instead, the issue was always secondary sanctions: those that Washington would impose on Iran's trade partners for their adherence to the agreement. That impact looks set to hurt U.S. allies as much as it does Iran.

U.S. President Donald Trump does not just seek an end to Iran's nuclear program. He withdrew from the agreement in May because he wants a transformation of the Iranian government's behavior, from its meddling in regional affairs to the way it treats its own people. Secretary of State Mike Pompeo warned that a failure to do so would result in the "strongest sanctions in history." Since U.S. trade with Iran in 2017 was a mere $200 million, inflicting pain on the country meant that the impact of sanctions would have to fall elsewhere.

China is Iran's largest trading partner: Their total trade was €23.8 billion in 2017. The European Union was Iran's third-largest trading partner, with total trade just under €20 billion; imports grew 89 percent in 2017, while exports expanded 31.5 percent. India was its fourth-largest trade partner (€9.8 billion), and South Korea was sixth (€9.0 billion). The goal of U.S. sanctions is to punish firms in those countries and force them to choose between doing business with Iran and the U.S.