© ReutersThe Iraqi Badr Organization, a militia led by Hadi al-Amiri, says it rejects U.S. designation of the IRGC.
The Tehran-backed groups on April 13 said from the home of Iran's consul-general in the Shi'ite holy city of Najaf that the IRGC had helped prevent four or five states from falling to Islamic State (IS) militants.
Some of the militia groups themselves have been designated as terrorist organizations by Washington.
"This is laughable coming from the No. 1 sponsor of terrorism, America," said a spokesman for the Badr Organization, which was part of the volunteer forces that helped to defeat IS along with Iraqi government troops and U.S.-backed Western coalition forces.
Badr is led by Iraqi militia commander and politician Hadi al-Amiri, whose Fateh coalition of militia groups has the second-largest number of seats in the Iraqi parliament.
"We reject this action from America and say we have honor to be in the Islamic resistance that fought and beat terrorism," a spokesman for the wider Fateh coalition said.
President Donald Trump on April 8 announced the decision to place the IRGC on the State Department FTO list, the first time the United States has designated a state entity of another government as a terrorist organization.
Iranian Supreme Leader Ayatollah Ali Khamenei said on April 9 that the United States had made "a vicious move," adding that the IRGC was at the "front line of confronting [the] enemies" of the Islamic republic.
Comment: Silver lining: Trump continues to push Iraq into the hands of Iran. Lebanon isn't far behind. Just remember who were the ones that actually defeated the bulk of the terrorists in Iraq and Syria: Iraqi Shia militias, the Syrian Army, the IRGC, Hezbollah, and the Russians. And remember those who sat back and did nothing, or actively supported the terrorists: the U.S., Israel, Saudi Arabia, Qatar, UAE, etc. The U.S. coalition, including the SDF, did take a lot of territory from ISIS, but only after years of letting them grow.