Iran’s Foreign Minister Mohammad Javad Zarif has written a letter to UN General Secretary Antonio Guterres to complain about Washington’s decision designating the Islamic Revolution Guard Corps (IRGC) as a “terrorist” organization.

In the letter published in Persian by the official news agency IRNA on Thursday April 11, Zarif has called the U.S. move “unprecedented, illegal and dangerous”.

The United States Designated the IRGC as a “Foreign Terrorist Organization” after years of repeated accusations that the Iranian military force was interfering in other countries and providing support to militant groups. Washington had previously sanctioned many entities and individuals linked with IRGC but had not formally designated it as a terror group.

In his letter, Zarif insists that the IRGC is an official military force and the U.S. decision violates international law and the charter of the United Nations.

He adds that the move fuels tensions in an already volatile region and accuses “two or three vassal regimes” of supporting the decision of the “American regime”.

Zarif informs Guterres that in a reciprocal move, Iran has designated “the U.S. regime” as a state-sponsor of terrorism and the U.S. Central Command, CENTCOM and all its affiliates as “terrorist group”.