Reuters - Iran will take reciprocal action against the United States if Washington designates the elite Revolutionary Guards (IRGC) as terrorists, a majority of Iranian parliamentarians said on Sunday, according to state news agency IRNA.

The United States is expected to designate the Revolutionary Guards a foreign terrorist organization, three U.S. officials told Reuters, marking the first time Washington has formally labeled 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.�

The U.S. decision, which critics warn could open U.S. military and intelligence officials to similar actions by unfriendly governments abroad, is expected to be announced by the State Department perhaps as early as Monday, the U.S. officials said last week. The move has been rumored for years.

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 Islamic State all around the world�.

U.S. Secretary of State Mike Pompeo, a strident Iran hawk, has advocated the change in U.S. policy as part of the Trump administration�s tough posture toward Tehran.

Set up after the 1979 Islamic Revolution to protect the Shi�ite 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.

Reporting by Babak Dehghanpisheh; Editing by Mark Heinrich