Washington (CNN) President Donald Trump announced Monday the US will formally designate Iran's Islamic Revolutionary Guard Corps as a Foreign Terrorist Organization, a move some in the administration had opposed over concerns about potential risks to US troops in the Middle East.

The step "recognizes the reality that Iran is not only a State Sponsor of Terrorism, but that the IRGC actively participates in, finances, and promotes terrorism as a tool of statecraft," Trump said in a statement that described the IRGC as "the Iranian government's primary means of directing and implementing its global terrorist campaign."

Administration officials said the move is a response to Iran's destabilizing behavior across the Middle East, including support for the regime in Syria, Houthi rebels in Yemen and Hezbollah in Lebanon, as well as for assassination plots in Europe and the US.

The announcement aims to drive a stake through the heart of a central institution in Iran. Formed after the Islamic revolution in 1979, the IRGC is not only Iran's most powerful military institution, it holds deep influence over domestic politics and the economy, with interests extending to and beyond the construction, telecommunications, auto and energy industries.

Iran responds

Beyond the internal dissent the designation triggered within the US government, the move could also increase tensions with allies, particularly Iraq , where the IRGC has ties to militias and officials, and Lebanon, where it backs Hezbollah, which is part of the government.

Iran's Supreme National Security Council responded Monday by declaring the US a "state sponsor of terrorism" and American troops operating in the region as "terrorist groups," according to IRNA, Iran's state-run news agency.

"The Islamic Republic of Iran declares itself in reciprocity against the unlawful and unreasonable action of the United States today, considering the United States as a terrorist sponsored government and the Central Command of the United States, CENTCOM, and all its affiliated forces as terrorist groups," the National Security Council of the Islamic Republic of Iran said in a statement, IRNA reported.

"Obviously, the US regime will take all the responsibility for the dangerous consequences of this undertaking," the statement said.

The IRGC designation marks the first time that the United States has ever named a part of another government as a foreign terrorist organization.

In an important step to counter the Iranian regime's terrorism, the U.S. has designated the Islamic Revolutionary Guard Corps, incl. Qods Force, as a Foreign Terrorist Organization. We must help the people of Iran get back their freedom. pic.twitter.com/T65CxJjRrr — Secretary Pompeo (@SecPompeo) April 8, 2019

It takes effect on April 15, Secretary of State Mike Pompeo told reporters at the State Department Monday.

Economic and travel sanctions on the elite military group mean any group or individual that does business with the IRGC could face criminal prosecution for providing material support to a terrorist organization.

"This historic step will deprive the world's leading state sponsor of terror the financial means to spread misery and death around the world," Pompeo said. He warned that businesses with a presence in Iran or engaged with its companies will have to take extra steps to ensure they are not violating US sanctions.

Brian Hook, a senior policy adviser to Pompeo, said Monday that the IRGC controls "up to half Iran's economy."

"It is absolutely the case that the IRGC amounts to a significant amount of the Iranian economy through pure kleptocracy," Pompeo said. "Businesses and banks around the world now have a clear duty to ensure that companies with which they conduct transactions are not connected to the IRGC in any material way."

Concerns about troops

Senior officials said the designation decision, formally under the State Department's purview, represents the next step in the Trump administration's maximum pressure campaign against Iran, but the move had met with internal resistance because of concerns about American troops in the Middle East.

Defense officials have told CNN that US troops in Syria and Iraq often find themselves operating in close proximity to members of the IRGC. The US has about 5,000 troops in Iraq and close to 2,000 in Syria.

Last year, CNN reported that Director of National Intelligence Dan Coats cautioned the administration that designating the IRGC could pose dangers to US forces, according to one source familiar with the matter.

Asked about the risks to US troops in the Middle East and particularly in Iraq, Hook told reporters at the State Department that "the decision leading up to this process was a full interagency process that included every member of the NSC. We have taken all measures that are appropriate and prudent in the context of this designation."

He added that "whenever we and other nations call out and expose the regime for what it is, it behaves like a mafia organization increasing its threats. We will not be deterred by their threats."

'Prepared'

Nathan Sales, the State Department's Coordinator for Counterterrorism, said the agency would not discuss details of measures being taken to ensure the safety of US personnel.

"I can assure you that we take force protection very, very seriously. And that is why we have run a robust interagency process to make sure that all interested parties are prepared for whatever the Iranian regime might throw at us," he said, speaking alongside Hook Monday.

Cmdr. Rebecca Rebarich, Pentagon spokeswoman, said Monday that "the Department of Defense is prepared to implement the President and Secretary of State's decision to designate the Islamic Revolutionary Guard Corps as a Foreign Terrorist Organization."

"As a matter of policy, we do not discuss adjustments to force protection levels or measures for operational security reasons," Rebarich continued. "As always, DoD has taken prudent measures to ensure the safety of our forces around the world, and maintain our readiness to carry out our missions."

#NetanyahuFirsters who have long agitated for FTO designation of the IRGC fully understand its consequences for US forces in the region. In fact, they seek to drag US into a quagmire on his behalf.@realDonaldTrump should know better than to be conned into another US disaster. pic.twitter.com/i4bcfgxybT — Javad Zarif (@JZarif) April 7, 2019

Mark Dubowitz, CEO of the Foundation for Defense of Democracies, said it was "fitting that the most dangerous terrorist group in the world, responsible for the deaths of tens of thousands of innocents and backed by a massive state apparatus and vast energy wealth, is being designated finally as a foreign terrorist organization."

The designation now means "the US government can truly unleash its full economic, prosecutorial and political powers" to punish Iran, Dubowitz said.

Trita Parsi, the author of "Losing an Enemy - Obama, Iran and the Triumph of Diplomacy," warned that the designation carries significant political implications and ultimately will not serve US security interests.

"This move closes yet another potential door for peacefully resolving tensions with Iran," Parsi said. "Once all doors are closed, and diplomacy is rendered impossible, war will essentially become inevitable ... this decision does not in any way shape or form serve US national security. On the contrary, it makes America less safe by making war more likely."

"Even if future administrations would want to resolve tensions with Iran, the spiderweb of sanctions and terrorism designations makes any meaningful movement towards a diplomatic breakthrough with Iran politically unfeasible in Washington," Parsi said.

Israeli reaction

The move was warmly welcomed by Israeli Prime Minister Benjamin Netanyahu, who thanked Trump in a tweet and appeared to take some credit for the move, which comes a day before Israeli elections.

"Thank you, my dear friend, President of the United States Donald Trump, for your decision to declare Iran's Revolutionary Guard as a terror organization," Netanyahu wrote. "Thank you for responding to another one of my important requests, that serves our interests and the interests of regional countries."

The IRGC designation follows Trump's March 21 announcement that the US would recognize Israeli control of the Golan Heights, a step that counters United Nations resolutions against land being seized by force. Like the President's decision to move the US embassy to Jerusalem and recognize the city as Israel's capitol, the Golan decision reversed decades of US policy and countered international norms.