Threat comes as Britain, France and US gear up for another push for sanctions resolution.
Iran on Sunday warned it would hit back with an appropriate response to new UN Security Council sanctions over its contested nuclear programme, as Western powers stepped up efforts to punish Tehran.
Britain, France and the US are pushing for a new sanctions resolution in the coming week after the UN atomic watchdog said it could still not confirm if the Iranian atomic drive was peaceful.
"In the case of the adoption of the resolution, we will make a deserving action. We will announce our decision at the right time based on the content of the resolution," Foreign Ministry spokesman Mohammad Ali Hosseini said.
President Mahmoud Ahmadinejad on Saturday warned of "firm reprisals" against any country leading the way to impose new sanctions, adding that Iran was "not joking".
"They could spend 100 years passing resolutions but it will not change anything," he said in an interview with state television.
Neither Hosseini or Ahmadinejad gave any details over exactly what Iran's response could involve.
The International Atomic Energy Agency (IAEA) said Friday in its latest report that it had made "quite good progress" in its four year-probe into the Iranian nuclear drive.
But crucially for future sanctions, the report said it was still not in a position to determine the "full nature of Iran's nuclear programme" and confirmed Tehran was continuing to defy UN demands by enriching uranium.
The report met with starkly different responses from Western capitals and Tehran.
Iranian officials said the report proved that the nuclear case was now closed, with Ahmadinejad hailing the "historic victory of Iran in its greatest confrontation with the oppressive powers since the Islamic revolution".
But US Secretary of State Condoleezza Rice said the report provided "a very strong case" for moving forward with a third UN Security Council sanctions resolution to punish Tehran's failure to suspend enrichment.
"It is our firm belief that there is all the more reason now for the Security Council to pass a third sanctions resolution," added US Assistant Secretary for Political Affairs Nicholas Burns.
Iran has defied calls in previous resolutions for it to freeze uranium enrichment operations, a sensitive process world powers fear could be used to make nuclear weapons.
Tehran insists its nuclear programme is peaceful and only aimed at generating atomic energy for a growing population whose immense oil and gas reserves will run out in decades.
Meanwhile, top Iranian cleric Akbar Hashemi Rafsanjani accused the US of unbalancing IAEA chief Mohamed ElBaradei's "mental state" by submitting secret documents just days before the report.
"The US has submitted a stack of documents to disrupt ElBaradei's mental state and has been successful to some extent," said the head of the elite clerical body the Assembly of Experts, according to the state IRNA agency.
Washington was to host a new round of talks between world powers on Monday ahead of a council meeting on Wednesday and a vote on the resolution text on Friday, US officials said.
The draft text has been brought forward by Britain and France and it remains to be seen how veto-wielding members China and Russia will respond. Four non-permanent members are also said to harbour reservations.
The draft would impose a travel ban on officials involved in Tehran's nuclear and missile programmes and inspections of shipments to and from Iran if there are suspicions they may contain prohibited goods.
But Hosseini brushed off the prospect of further sanctions, saying that they could only cause "slight problems" for the Islamic republic.
Israel, Iran's arch regional enemy which accuses Tehran of seeking a nuclear weapon, again called for tougher action against the Islamic republic.
"Iran is still a threat to the world, it still wants a nuclear weapon and we have to act against that and against companies cooperating with Iran," Deputy Prime Minister Haim Ramon told public radio.