United States President Donald Trump has designated Iran's elite Revolutionary Guard Corps (IRGC) as a foreign terrorist organization. It is the first time the US has labelled another nation's military as a terrorist organization. Iran retaliated by declaring US forces in the Middle East as a terrorist organization, Iran state news reported.
Washington-Tehran tensions have risen since Mr. Trump withdrew the US from the international Iran nuclear pact.
Labeling the Guards as a terrorist organization will allow the US to impose further sanctions - particularly affecting the business sector, given the IRGC's involvement in Iran's economy.
A number of IRGC and affiliated entities have already been targeted by US sanctions for alleged proliferation activities, support for terrorism and human rights abuses.
Trump's statement on Monday said: This unprecedented step, led by the Department of State, recognizes 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.
The president added that the move was meant to significantly expand the scope and scale of pressure on Iran. If you are doing business with the IRGC, you will be bankrolling terrorism, Mr. Trump said.
The measure will take effect in one week's time, according to the State Department.
US Secretary of State Mike Pompeo and National Security Adviser John Bolton, both Iran hawks, championed the decision, but not all US officials were so supportive.
Some Pentagon officials, including Joint Chiefs of Staff Chairman Gen Joe Dunford, had expressed concerns about troop safety, the Wall Street Journal reported.
Military officials cautioned the designation could incite violence against US forces in the Middle East without severely impacting Iran's economy.
The Central Intelligence Agency had also reportedly opposed the move.
Iran's national Security Council declared US Central Command (Centcom) a terrorist organization after Foreign Minister Javad Zarif wrote to President Hassan Rouhani urging such a response, state news channel IRINN said.
Centcom is the Pentagon wing that oversees Washington's security interests across the central area of the world map, most notably Afghanistan, Iraq, Iran, Pakistan and Syria.
The Islamic Republic had warned it would retaliate in kind last week, after reports of the Trump administration plan first surfaced.
We will answer any action taken against this force with a reciprocal action, a statement issued by 255 out of the 290 Iranian MPs said, according to the state-run IRNA news agency.
Iran's most elite military unit, the IRGC was set up shortly after the 1979 Iranian revolution to defend the country's Islamic system, and to provide a counterweight to the regular armed forces. It has since become a major military, political and economic force in Iran, with close ties to the Supreme Leader, Ayatollah Ali Khamenei, and many other senior figures hailing from its ranks.
The IRGC is estimated to have more than 150,000 active personnel, boasts its own ground forces, navy and air force, and oversees Iran's strategic weapons, including its ballistic missiles.
The IRGC exerts influence elsewhere in the Middle East by providing money, weapons, technology, training and advice to allied governments and armed groups through its shadowy overseas operations arm, the Quds (Jerusalem) Force.