In a letter to the United Nations Secretary General Antonio Guterres on Sunday, Zarif described "the illegal, dangerous and provocative US threats [against the Iranian tankers]" as a form of piracy and a big threat to international peace and security.
Iran's foreign minister added that the US must stop acting as a bully at international level and respect teh rule of international laws, in particular the right to free shipping in free waters.
The top Iranian then highlighted the responsibility of "the US administration with regard to the consequences of any illegal move, reiterating Iran's right right to adopt appropriate and necessary measures in the face of such threats.
Iran summons Swiss ambassador over US threat to tankers
Following Zarif's letter, Iran's Deputy Foreign Minister for Political Affairs Abbas Araqchi summoned the Swiss envoy, whose country represents US interests in Tehran, to voice the country's vehement protest at US provocations.
He called on the Swiss diplomat to convey the Islamic Republic's serious warning to the American officials against any possible threat posed by the US to the Iranian oil tankers.
Araqchi noted that Iran and Venezuela enjoy "completely legitimate and legal trade relations," adding that the US recourse to forceful or other forces of bullying measures will be seen as a threat to "free shipping, international trade and the free flow of energy."
Such measures, the Iranian deputy foreign minister said, are blatant examples of piracy and explicit violation of international laws and, as such, contravene the goals and principles enshrined in the UN Charter.
The top Iranian diplomat also warned that any threat against the country's tankers will elicit Iran's immediate and categorical reaction, and the US administration will be responsible for their consequences.
The Swiss envoy, for his part, said he will immediately convey the Islamic Republic’s message to the US administration and inform the Iranian government of the results as soon as possible.