The United States is expected to designate Iran's elite Revolutionary Guard Corps a foreign terrorist organization, three U.S. officials said, marking the first time Washington has formally labeled another country's military a terrorist group.

The 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 U.S. State Department, perhaps as early as Monday, the officials said. It has been rumored for years.

The Pentagon declined comment and referred queries to the State Department. The State Department and White House also declined to comment.