Officials from Iran's Revolutionary Guards (IRGC) have denounced reported US plans to designate the force as a foreign terrorist unit as "worthless".
The guards force was established after the Islamic revolution in 1979
But an unnamed Iranian foreign ministry official said it was too early to comment officially because Tehran had not been told about the possible move.
The EU said it had no plans to add the IRGC to its list of terror groups.
The US accuses the guards of helping to destabilise Iraq and Afghanistan by supplying and training insurgents.
The classification would allow the US to target the force's finances.
Officials in Washington have said this week that the US might classify all or part of the IRGC as a terror group.
If confirmed, it would be the first time official armed units of a sovereign state have been included in the US list of banned terrorist groups.
In a statement published by Iran's Mehr news agency, the IRGC condemned the plan as "worthless resolutions" issued "dauntlessly and under baseless pretexts... to damage this holy institution".
"Those who are enchanted by the material world fail to realise the depth of the spiritual power and iron determination of the devoted members of the IRGC, which have roots in the religious beliefs of the people, and will witness the definite victory of the children of Islam against global infidelity," the statement said.
The foreign ministry official dismissed reports of the plan as part of an ongoing US psychological and propaganda war against Iran.
Officially the Islamic Revolution Guards Corps (IRGC), or Pasdaran
Formed after 1979 revolution
Loyal to clerics and counter to regular military
Estimated 125,000 troops
Includes ground forces, navy, air force, intelligence and special forces
Also has political influence: dozens of ex-guard sit as MPs
Iran President Ahmadinejad is a former member
Other Iranian MPs have been quoted in state media defending the guards.
One MP told Iranian state radio that if the US designated the guards it would show that the terrorist listings were decided on a completely political basis.
European Commission spokesman Jens Mester told AFP news agency that the EU usually added organisations to its list of banned terrorist groups only after a UN decision.
The EU made such decisions independently of the US, he stressed.
There are 42 organisations on the US state department's list of foreign terrorist groups, including al-Qaeda, Lebanese militant group Hezbollah and Palestinian groups Hamas and Islamic Jihad, as well as Sri Lanka's Tamil Tigers and Basque separatist group Eta.
Correspondents say Washington views the guards force as a state within a state, which has tentacles in business activities and is involved in Iran's nuclear programme.
The move is intended to increase the pressure on Iran amid growing concern in Washington that Tehran is funding and supporting insurgents in Iraq, the Taleban in Afghanistan and Hezbollah, US officials have said.
The Revolutionary Guards force was established after the Islamic revolution toppled the Shah and brought hard-line clerics to power in Iran in 1979.
It is estimated to have 125,000 active members, and operates separately from Iran's main armed forces, boasting its own ground forces, navy, air force, intelligence and special forces capability.