The US has designated Iran’s Islamic Revolutionary Guard Corps as a terrorist organisation.
President Donald Trump’s decision to sanction the IRGC, which is a branch of Iran’s Armed Forces, is designed to increase pressure on the country.
It is the first time the US has designated an official body of another country as a terrorist organisation.
“This unprecedented step, led by the Department of State, recognises the reality that Iran is not only a state sponsor of terrorism, but that the IRGC actively participates in, finances, and promotes terrorism as a tool of statecraft,” Mr Trump said in a statement.
Iran’s state TV says the move is illegal.
Without quoting a specific official, the channel said: “No other country has the legal right to designate as terrorist another country’s armed forces… Iran’s influence in the Middle East and its success in fighting against Islamic State are reasons behind this designation.”
The IRGC was founded after Iran’s 1979 Islamic Revolution and answers only to Iran’s supreme leader, currently Ali Khamenei.
It operates independently of the regular military and has wide-ranging economic interests across the country.
The designation, which will come into effect next week, imposes sanctions on the group.
Any assets the Islamic Revolutionary Guard Corps may have in US jurisdictions will be frozen and Americans will be banned from doing business with it.
People who have provided the group with support will potentially be barred from entering the US.
If no waivers are included in the designation the move is likely to complicate diplomacy in the region, with figures from other counties who interact with the Guard potentially being barred from talking to US authorities or troops.
Writing in Hebrew, Israel’s prime minister Benjamin Netanyahu tweeted support for Mr Trump’s decision, saying: “Thank you, my dear friend… for having decided to announce Iran’s Revolutionary Guards as a terrorist organisation. Thank you for the answer to another important request that serves the interests of our country and the region.
“We will continue to act together in any way against the Iranian regime that threatens the state of Israel, the United States and the peace of the world.”
The clampdown on the Guard is the latest in a series of actions the US has taken against Iran since Mr Trump became president in 2016, most notably withdrawing from a nuclear deal.