Designating Islamic Revolution Guard Corps (IRGC) as a terrorist group is an explicit sign of an old grudge and discloses the stupidity of the US regime, Iran's Parliament Speaker said Tuesday.

The shameful act of the US to call the IRGC a terrorist group shows that the regime of Washington is holding an old grudge on the forces, Ali Larijani said at the open session of the Iranian parliament.

The U President Donald Trump on Monday officially labeled IRGC, a part of Iran's Armed Forces, a terrorist organization.

'Who does not know that IRGC has inflicted the harshest blows to the dreadful terrorist groups in the region?,' Larijani added in a reference to the terrorist group of Daesh (ISIS) that took control of vast areas in Iraq and Syria after its emergence in 2014 but was defeated through Iran's efforst.

The Iranian forces in coordination with governments in Iraq and Syria has played a military advisory role in fighting the terrorist group in both countries. Iraq in 2017 officially announced the defeat of Daesh, while Syria has managed to retake most of the fallen areas from the terrorists.

Referring to the eight-year war with former Iraqi regime, the speaker described IRGC as the main pillar of resistance during the years.

The latest anti-Iran move of Trump received fierce reactions from Iranian officials. The country's Foreign Minister Javad Zarif in a letter to President Hassan Rouhani called for a retaliatory move by labeling the United States Central Command (CENTCOM) as a terrorist organization and the US government as a terrorist sponsor.

Zarif also called the move as 'another misguided election-eve gift to Netanyahu”.

The members of Iranian parliament at Tuesday's session, coincided with the Iranian national day of Guards, showed up in official uniforms of IRGC to announce their support and solidarity with the forces.