The move could be announced as early as Monday, April 8, according to WSJ. If carried out, it will mark the first time another country's military has been branded as a terrorist group. Reuters reports that three sources close to the matter confirmed the WSJ account to them, and that US Secretary of State Mike Pompeo has been pushing for the new designation.
The IRGC is already sanctioned by the US: the Department of Treasury imposed sanctions on the military organization in October 2017 under a 9/11-era executive order issued during the George W. Bush administration.
"The IRGC has played a central role to Iran becoming the world's foremost state sponsor of terror. Iran's pursuit of power comes at the cost of regional stability, and Treasury will continue using its authorities to disrupt the IRGC's destructive activities," Treasury Secretary Steven T. Mnuchin said at the time.
"We are designating the IRGC for providing support to the IRGC-QF, the key Iranian entity enabling Syrian President Bashar al-Assad's relentless campaign of brutal violence against his own people, as well as the lethal activities of Hizballah, Hamas, and other terrorist groups. We urge the private sector to recognize that the IRGC permeates much of the Iranian economy, and those who transact with IRGC-controlled companies do so at great risk."
Per the US Department of State, designating a group a foreign terrorist organization is "an effective means of curtailing support for terrorist activities and pressuring groups to get out of the terrorism business." The most recent group to be added to the list is the militant jihadist organization Jama'at Nusrat al-Islam wal-Muslimin. It was added on September 6, 2018.
The decision to designate a group a terrorist organization is done in consultation between the secretary of state, US attorney general and the secretary of the treasury. Once the decision is agreed to by the trio, Congress is notified and given seven days to review the move. After the seven-day waiting period comes to a close, and lawmakers do not block the decision, notice of the designation is published in the Federal Registrar and goes into effect. The designated organization, however, can ask for the designation to be reviewed by a US appeals court within 30 days of the official pronouncement.
Relations between the US and Iran in recent months hit a new low after the Trump administration pulled out of the Joint Comprehensive Plane of Action (JCPOA) in May 2018, triggering the reactivation of a series of sanctions against the Middle Eastern country. A senior Trump official indicated this week that the administration was considering the possibility of introducing further sanctions next month. On Tuesday, US Special Representative for Iran Brian Hook blamed Iran for the deaths of more than 600 US servicemembers during the Iraq War.