(JTA) — The United States will designate Iran’s Revolutionary Guards Corp as a foreign terrorist organization.

The designation, which is expected to be announced by the State Department on Monday, would be the first time that the military of another country is designated as a terror group by the U.S., Reuters reported. Three U.S. officials confirmed the plan to Reuters, according to the news service.

Former Under-Secretary of State and lead Iran negotiator, Wendy Sherman, said the announcement “absolutely endangers” U.S. troops in the region. She told Reuters it is “hard to see why this is in our interest.”

The semi-official government news agency Fars reported that IRGC Top Commander Maj.-Gen. Mohammad Ali Jafari issued a tough warning to U.S. President Donald Trump.

“If reports prove to be true that the stupid U.S. administration intends to designate the IRGC as a terrorist organization, the U.S. Army and American security forces stationed in West Asia (Middle-East) will lose their current status of ease and serenity,” Jafari said, according to Fars. “If they make a stupid move as such and endanger our national security, a reciprocal move will be placed on our agenda and then put into operation.”

Hossein Nekwai Hosseini, a member of the National Security and Foreign Policy Committee of the Iranian Islamic Affairs Council, said lawmakers are preparing a draft law that considers the U.S. military in the region a terrorist organization, in response to Washington’s possible inclusion of the Revolutionary Guards on the list of terrorist groups, Fars reported Sunday.