The move would mark the first time Washington formally labels another country’s military a terrorist group.
The decision, which critics warn exposes US military and intelligence officials to similar actions by unfriendly governments abroad, is expected to be announced by the US State Department as early as Monday, the officials told the Wall Street Journal.
The change of designation has been rumoured for years.
The Pentagon declined comment and referred queries to the State Department. The State Department and White House also declined to comment.
The Iranian mission to the United Nations did not immediately respond to a request for comment.
US Secretary of State Mike Pompeo, a strident Iran critic, has advocated for the change in US policy as part of the Trump administration’s tough posture toward Tehran.
The announcement would come ahead of the first anniversary of President Donald Trump‘s decision to pull out of a 2015 nuclear deal with Tehran and to reimpose sanctions that had crippled Iran’s economy.
The United States has already blacklisted dozens of entities and people for affiliations with the IRGC, but the organisation as a whole is not.
The latest sanctions were imposed in March on a network of companies and individuals said to be transferring billions of dollars and euros to IRGC.
In 2007, the US Treasury designated the IRGC’s Quds Force, its unit in charge of operations abroad, “for its support of terrorism,” and has described it as Iran’s “primary arm for executing its policy of supporting terrorist and insurgent groups”.
Implications of move
Iran has warned of a “crushing” response should the US goes ahead with the designation.
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”.
Such threats are particularly ominous for US forces in places such as Iraq, where Iran-aligned Shia militia are located in close proximity to US troops.
Republican Senator Ben Sasse said the move would be an important step in the US’s maximum pressure campaign against Tehran. “A formal designation and its consequences may be new, but these IRGC butchers have been terrorists for a long time,” Sasse said in a statement.
“There are legitimate arguments both ways, but there are definitely second and third-tier level (implications) that have to be considered,” a US official told the Wall Street Journal.
Those who have argued against the move, “think those second and third-tier levels haven’t been fully considered”.
“New leadership has decided to look at things differently,” added the official.
Former Under-Secretary of State and lead Iran negotiator, Wendy Sherman, said she worried about implications for US forces.
“One might even suggest, since it’s hard to see why this is in our interest, if the president isn’t looking for a basis for a conflict,” said Sherman, who is director of the Center for Public Leadership at the Harvard Kennedy School.
“The IRGC is already fully sanctioned and this escalation absolutely endangers our troops in the region.”
Revolutionary Corp reach
Set up after the 1979 Islamic Revolution to protect the Shia clerical ruling system, the IRGC is Iran’s most powerful security organisation. It has control over large sectors of the Iranian economy and has a huge influence in its political system.
The IRGC is in charge of Iran’s ballistic missiles and nuclear programmes. Tehran has warned that it has missiles with a range of up to 2,000km, putting Israel and US military bases in the region within reach.
The IRGC has an estimated 125,000-strong military with army, navy and air units and answers to Supreme Leader Ayatollah Ali Khamenei.
Al Jazeera and news agencies