Relations between the two countries have deteriorated sharply since April
On April 8t, the US administration labelled Iran’s elite Revolutionary Guard Corps as a foreign terrorist organisation.
On April 22, the USA ended exemptions from sanctions for eight countries (China, India, Italy, Greece, Japan, South Korea, Taiwan and Turkey) still buying oil from Iran.
On May 8, the USA unveiled new sanctions against the Iranian mining and steel sectors. In retaliation, Iranian President Rohani announced the same day that Iran will no longer comply with two of its JCPOA obligations: the country will stop exporting its surplus of enriched uranium and heavy water, which means that at some point it will exceed the ceiling of stock authorised by this multilateral nuclear accord.
In addition, if other signatories of the agreement (notably Europe) do not help Iran economically, the country threatens not to respect other constraints related to its nuclear programme. In other words, Iran could enrich uranium for military purposes again, which could be interpreted as a casus belli, an event that justifies war, by Washington.
In recent days, the United States has announced the dispatch of military forces in the region, including the deploying of the USS Abraham Lincoln aircraft carrier and the USS Arlington assault ship.
How to explain this sudden increase of tensions?
As a reminder, new US sanctions against Iran were unveiled in November 2018, with targets including 50 banks and their subsidiaries and 200 members of the shipping industry and some restrictions against oil exports (excepting the eight countries mentioned above).
Iran has certainly been slow to react to these new US sanctions for two main reasons: (1) the Iranian regime believed that President Trump would not be re-elected next year, which is getting less and less certain, and (2) it believed that the other JCPOA signatories would help the country economically in order to offset the impact of the US withdrawal from the agreement and US new sanctions. Europe has launched INSTEX to bypass US sanctions but with little effect on trade and the Iranian economy so far. The two other signatories, Russia and China, do not seem eager to engage in a diplomatic standoff. China is even looking to reduce the amount of Iranian oil it is buying, likely in CNY, in order not to increase confrontation with the US.