The designation also risks impacting USA relations with countries in the region that have direct relations with the Iranian government, including Lebanon and Iraq, where Shia-led armed groups are supported by the IRGC and are represented in the governments of those countries.
The United States put Iran's Islamic Revolutionary Guard Corps on its list of terrorist groups on Monday.
Critics have warned the move could subject U.S. military and intelligence officials to similar actions by other governments.
The US has already blacklisted dozens of entities and people for affiliations with the IRGC, but not the organisation as a whole.
The Trump Organization was informed in 2015 that its partners, the Mammadov family of Azerbaijan, were likely laundering money for Iran's Revolutionary Guard. "A (nother) risky US misadventure in the region", he wrote.
"If [the Americans] make such a stupid move, the U.S. Army and American security forces stationed in West Asia will lose their current status of ease and serenity", he said Sunday, according to Iranian state news service Fars.
The US and its regional allies such as Saudi Arabia and Israel accuse Iran of trying to destabilise the region in part by using IRGC and its affiliated Quds force, which played a pivotal role to defeat Daesh in Iraq.
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Unlike the 2017 Equifax breach, financial details and Social Security numbers were left out. UpGuard also found data through a backup for a Facebook-linked app called " At the Pool ".
But Israeli Prime Minister Benjamin Netanyahu, who is battling for political survival in Tuesday's elections, cheered the USA move.
"This designation is a direct response to an outlaw regime and should surprise no one", he said.
The Revolutionary Guard was created in parallel to the country's existing armed forces to consolidate power under Ayatollah Ruhollah Khomeini in the 1979 Islamic Revolution.
It also influences Iran's foreign policy such as decisions around its intervention in Syria, something that reportedly prompted Iran's foreign minister, Javad Zarif, to resign earlier this year; Rouhani didn't accept his resignation. Thousands of USA troops in the region, especially in Iraq and Syria where they operate close to Iranian-organized militias or IRGC personnel, will now have targets on their back if Tehran decides to respond militarily to the designation.
The IRGC terrorist designation is a political and symbolic decision with no upsides and plenty of potentially risky consequences for USA interests in the Middle East.
Military officials cautioned the designation could incite violence against USA forces in the Middle East without severely impacting Iran's economy.
Bahrain, led by a Sunni Muslim royal family, has accused Shi'ite Muslim Iran of supporting Shi'ite anti-government groups on its territory.
The IRGC is estimated to have more than 150,000 active personnel, boasts its own ground forces, navy and air force, and oversees Iran's strategic weapons, including its ballistic missiles.
Iran has warned it will take reciprocal action against Washington for its move against the Guards, the country's most powerful security organization. The U.S. estimates it may control or have a significant influence over up to 50% of the Iranian economy, including non-military sectors like banking and shipping. Tehran has warned that it has missiles with a range of up to 2,000 km (1,242 miles), putting Israel and USA military bases in the region within reach.