A spokesman for Iran’s Foreign Ministry said on Monday that the United States would be making a “strategic mistake” by designating Iran’s Islamic Revolutionary Guard Corps (IRGC) a terrorist organization.

“If they do, Iran’s reaction would be firm, decisive, and crushing and the United States should bear all its consequences,” the spokesman said.

Reuters reports that IRGC commander Mohammad Ali Jafari gave an even more incendiary statement on Sunday, implying Iran would physically attack U.S. troops in retaliation.

“If the news is correct about the stupidity of the American government in considering the Revolutionary Guards a terrorist group, then the Revolutionary Guards will consider the American army to be like Islamic State all around the world,” Jafari said.

Jafari further threatened American bases with missile attacks, saying that, if the U.S. designates the IRGC as terrorists, America will be obliged to move its bases outside the range of IRGC missiles.

“The Americans should know that the Islamic Republic would use the Trump administration’s stupid behavior toward JCPOA to make great strides in advancing its defensive, regional and missile programs,” Jafari warned, referring to President Trump’s reported plans to decertify the Iran nuclear deal, formally known as the Joint Comprehensive Plan of Action or JCPOA.

Reuters speculates that Iran’s anger was partially fueled by a Trump interview with Mike Huckabee, father of Press Secretary Sarah Huckabee Sanders, broadcast on Saturday night. In the interview, Trump said he was “very unhappy” with the Iran nuclear deal and is considering a range of responses to Iran’s bad behavior across the Middle East.

“They’re literally causing trouble, predominantly in the Middle East,” Trump said of Iran. “I believe they’re funding North Korea … that doesn’t pertain to the deal but, in my opinion, it does because it’s called the spirit of a deal … You will see what I will be doing but Iran is a bad player and they will be dealt with as a bad player.”

A senior administration official was quoted by the Financial Times on Friday predicting that President Trump would declare the IRGC a terrorist organization, along with new sanctions and a tough stance against Tehran’s proxy forces across the Middle East, as part of an “integrated Iran strategy focused on neutralizing and rolling back Iran’s malign activities regionally and globally.”

Another Financial Times source anticipated “stepped-up covert action against Iran and its proxies” as part of the Trump strategy.

Although it is commonly identified as the “Iranian Revolutionary Guards Corps” in Western media, the actual name of the organization is Islamic Revolutionary Guard Corps. Iranian law establishes the IRGC as “an institution commanded by the Supreme Leader whose purpose is to protect the Islamic Revolution of Iran and its accomplishments” and strive constantly to “spread the sovereignty of God’s law.”

It is an explicitly ideological military organization loyal to the “hardline” ayatollahs, which enables the “moderate” secular government of Iran to claim it has no ability to rein in the IRGC. Most confrontations between U.S. forces in the region and Iranian craft behaving in an irresponsible, aggressive manner involve the IRGC.

The IRGC is virtually a government unto itself, commanding so many resources that it has been rated one of the three wealthiest organizations in Iran. One of the strongest arguments for formally designating the Revolutionary Guard a terrorist organization is that it would stymie the IRGC’s effort to take control of most of Iran’s economy, an agenda deceptively labeled “privatization” by the Iranian theocracy. From this perspective, the Iran nuclear deal greatly empowered and enriched the IRGC by giving it a piece of the action when sanctions were lifted and Western companies resumed doing big business with Iran.

The IRGC includes an especially notorious unit called the Quds Force, which specializes in destabilizing foreign governments and arming insurgent groups. To this day, Quds Force leaders openly brag about killing American troops during the occupation of Iraq. The U.S. Treasury Department states the Quds Force has provided “material support to the Taliban and other terrorist organizations.”

Designating the entire IRGC a terrorist organization is an idea that has been considered since the earliest days of the Trump administration. If the policy is implemented, it will be the first time the Foreign Terrorist Organizations law has been applied to a foreign government institution, which could invite legal challenges. Since material support for a foreign terrorist organization is prohibited, the move would effectively forbid commerce with a large segment of the Iranian economy.

Critics also fear the terrorist designation could make it very difficult for U.S. forces to work with militia groups linked to the IRGC, as has been necessary with Shiite militias fighting the Islamic State in Iraq. Also, while this strongest of sanctions would significantly hurt the IRGC’s finances, there are concerns it could tip the balance of political power toward the “hardline” faction of the Iranian government.