LONDON: Iran said on Tuesday that the United States would be ?joining the terrorists? camp? if it chose to designate its elite Revolutionary Guards (IRGC) a terrorist organization.

US President Donald Trump is expected to announce this week his final decision on how he wants to contain Iran?s regional influence. He is also expected to designate Iran?s most powerful security force, the Islamic Revolutionary Guards Corp as a terrorist organization.

?The world should be thankful to the Revolutionary Guards for its fight against terrorists, especially against Daesh (Islamic State),? Iranian government spokesman Mohammad Baqer Nobakht said in a weekly news conference broadcast live on state television.

?So by taking a stance against the Revolutionary Guards and designating it a terrorist group, the Americans would be joining the terrorists? camp,? he added.

Trump is expected to ?decertify? a landmark 2015 deal Iran struck with world powers to curb its nuclear program in return for the lifting of most international sanctions.

Trump?s announcement would stop short of pulling out of the agreement but give Congress 60 days to decide whether to reimpose sanctions.

US sanctions on the IRGC could affect conflicts in Iraq and Syria, where Tehran and Washington support warring parties that oppose the Islamic State militant group.

IRGC commander Mohammad Ali Jafari said on Sunday that if Washington designated the Guards a terrorist organization, they ?will consider the American army to be like Islamic State all around the world.?

Iran?s Foreign Ministry spokesman Bahram Qasemi said on Monday that Tehran would give a ?firm, decisive and crushing? response if the United States goes ahead with such a plan.