Iran will take reciprocal action against the U.S. if Washington designates the elite Revolutionary Guards (IRGC) as terrorists, a majority of Iranian parliamentarians said yesterday, according to state news agency IRNA.

The United States is expected to designate the IRGC a foreign terrorist organization, three U.S. officials told Reuters, marking the first time Washington has formally labelled another country's military a terrorist group.

"We will answer any action taken against this force with a reciprocal action," a statement issued by 255 out of the 290 Iranian lawmakers said, according to IRNA. "So the leaders of America, who themselves are the creators and supporters of terrorists in the [Middle East] region, will regret this inappropriate and idiotic action."

IRGC commander Mohammad Ali Jafari warned in 2017 that if Trump went ahead with the move, "then the Revolutionary Guards will consider the American army to be like [Daesh] all around the world." "With this stupidity, the American army and security forces will no longer have today's calm in the west Asia region," Jafari was quoted as saying.

The long enmity between Iran and the U.S. worsened further following President Donald Trump's decision last year to pull out of an international accord curbing Tehran's nuclear program and to reimpose economic sanctions on Iran.

Set up after the 1979 Islamic Revolution to protect the Shiite clerical ruling system, the IRGC is Iran's most powerful security organization. It controls large sectors of the Iranian economy and has huge influence in its political system.