A former counterterrorism official is warning that removing Iran's Islamic Revolutionary Guard Corps (IRGC) from the Foreign Terrorist Organization (FTO) list would be a "colossal mistake" -- just as the Biden administration is considering such a move as it works to restore the Iran nuclear deal.

"Removing the IRGC from the list of designated Foreign Terrorist Organizations (FTOs) would be a colossal mistake, Nathan Sales, a former State Dept. counterterrorism coordinator who was part of the effort to list the IRGC in 2019, told Fox News.

BIDEN ADMIN CONSIDERING REMOVING IRAN'S IRGC FROM TERROR LIST AS PART OF IRAN DEAL TALKS: SOURCES

March 08, 2020: A huge mural of Ayatollah Seyyed Ali Khamenei Iran's Supreme Leader painted next to a smaller one of Ayatollah Ruhollah Khomeini (R) seen on Motahari street in Tehran, Iran.  (Photo by Kaveh Kazemi/Getty Images)

March 08, 2020: A huge mural of Ayatollah Seyyed Ali Khamenei Iran's Supreme Leader painted next to a smaller one of Ayatollah Ruhollah Khomeini (R) seen on Motahari street in Tehran, Iran.  (Photo by Kaveh Kazemi/Getty Images)

Two sources familiar with ongoing deliberation told Fox News last week that the administration is considering removing the IRGC -- which serves as a powerful military faction for the regime -- from the list. Tehran has been demanding such a concession for months as talks continue in Vienna for how to bring Iran and the U.S. back into the 2015 Joint Comprehensive Plan of Action (JCPOA).

The sources told Fox that such a move is under consideration but no decision has yet been made. Officials have noted that there'd still be other sanctions still in place on the IRGC if the FTO designation was lifted.

The FTO designation was put in place by the Trump administration in 2019 after it left the deal a year earlier. The administration also launched a strike to take out IRGC’s Gen. Qassem Soleimani, who headed up its paramilitary Quds Forces.

IRANIAN DISSIDENTS WARN THAT REMOVING IRGC'S TERROR DESIGNATION WILL LEAD TO ‘TERRORISM AND MAYHEM’

A senior administration official told Fox on Wednesday: "We don’t have a deal yet, and we’re not going to discuss anonymous speculation. We’re consulting with allies and partners, including Israel as we negotiate."

The official said that President Biden "will make a decision on whether to re-enter the deal based on what’s in the best interest of American security." 

Concerns have been raised about the move, including from Republican lawmakers and Iranian dissidents, that it would empower a wing of the regime that is central in fomenting terrorism and instability in the region and elsewhere.

"The IRGC has perpetrated terrorism around the world and has the blood of hundreds of Americans on its hands," Sales said. "Delisting the group would make it harder to prosecute its operatives and supporters, and harder to keep them from entering our country."

Reports of a potential delisting of the IRGC is already causing objection from U.S. allies. Israeli Prime Minister Naftali Bennett on Sunday said that his government is "very concerned about the United States’ intention to give in to Iran’s outrageous demand and remove the IRGC from the list of terrorist organizations."

"We are very concerned about the United States’ intention to give in to Iran’s outrageous demand and remove the IRGC from the list of terrorist organizations," Bennett said at a cabinet meeting.

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"This is not just an Israeli problem," he said, according to The Times of Israel. "Other countries – allies of the United States in the region – face this organization day in and day out… even now, the IRGC terrorist organization is trying to murder certain Israelis and Americans around the world."

"Unfortunately, there is still determination to sign the nuclear deal with Iran at almost any cost – including saying that the world’s largest terrorist organization is not a terrorist organization," he said. "This is too high a price."