The US has designated Iran & # 39; s Islamic Revolutionary Guards as a terrorist organization, prompting Iran to do the same with the US military.
President Donald Trump's decision to sanction the IRGC, which is part of the Iranian armed forces, is intended to increase pressure on the country.
It is the first time that the US has designated an official body of another country as a terrorist organization.
"This unprecedented move, led by the Ministry of Foreign Affairs, recognizes the reality that Iran is not only a state sponsor of terrorism, but that the IRGC is actively participating in, financing and promoting terrorism as a tool for statesmanship," said Mr. Trump in a statement.
The Iranian state television says the move is illegal.
Without quoting a specific official, the channel said: "No other country has the legal right to designate the forces of another country as a terrorist … the influence of Iran in the Middle East and its success in the fight against Islamic State are reasons for this designation. "
Shortly after the announcement was made, the Supreme Security Council of Iran designated the military forces of America as a terrorist organization.
The IRGC was established after the Islamic Revolution of Iran in 1979 and only meets the highest leader of Iran, currently Ali Khamenei.
It operates independently of the regular army and has broad economic interests throughout the country.
The designation, which takes effect next week, imposes sanctions on the group.
All assets that the Islamic Revolutionary Guard may have in US jurisdictions will be frozen and Americans will be banned from doing business with them.
People who have supported the group may be denied entry to the US.
If no exemptions are included in the designation, the move is likely to complicate diplomacy in the region, with figures from other countries in contact with the Guard and possibly being blocked from talking to US authorities or troops.
In Hebrew, Israeli Prime Minister Benjamin Netanyahu wrote support for Mr. Trump's decision: "Thank you, my dear friend … for deciding to announce the revolutionary guard of Iran as a terrorist organization." Thank you for responding to another important request that serves the interests of our country and the region.
"We will continue to act together in every 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 last in a series of actions that the US has taken against Iran since Mr. Trump became president in 2016, in particular withdraw from a nuclear deal.