Foreign Ministry spokesman Mohammad Ali Hosseini also said Iran was pressing ahead with an expansion of its uranium enrichment work and planned to install 3,000 centrifuges by March 2007, despite U.N.
demands to halt the endeavour.
The West fears Iran is trying to develop atomic weapons. Iran, the world's fourth largest oil exporter, says its programme is designed to meet energy needs.
Iran has two experimental chains of 164 centrifuges, which can make fuel for power plants or material for warheads. That number would take many years to yield enough material for one warhead. Iran says the thousands planned are for peaceful use.
With 3,000 centrifuges running, Iran could produce enough highly enriched uranium for one bomb within a year.
But U S nuclear expert David Albright said Iran did not appear close to launching that many centrifuges. ''It is not even established that Iran has all the necessary equipment to install 3,000,'' he said in an analysis published on November 9.
Israeli Prime Minister Ehud Olmert started a visit to Washington today with Tehran's nuclear programme one of the main issues on the agenda.
Israeli officials have said they want the international community, which has been pushing Iran to halt its atomic work, to resolve the dispute through diplomatic means.
But Israel bombed Iraq's Osirak nuclear reactor in 1981 to prevent then-President Saddam Hussein from assembling atomic weapons, and some analysts have speculated that Israel could consider similar action against Iran if it felt threatened.
Experts say knocking out Iran's nuclear facilities would be a far tougher prospect than it was in Iraq, partly because Iranian sites are spread out and heavily defended.
''If Israel takes such a stupid step and attacks, the answer of Iran and its Revolutionary Guard will be rapid, firm and destructive and it will be given in a few seconds,'' Hosseini told a news conference.
The Guards are an ideologically driven wing of Iran's military with a command structure separate from regular units.
Iranian President Mahmoud Ahmadinejad has said Israel should be ''wiped off the map'' but also that Iran is no threat. Iran refuses to recognise the Jewish state.
REJECTING DEMANDS Israel is widely believed to have the West Asia's only nuclear arsenal, though it has never said it possesses such weapons. Iran often complains about Western double standards in failing to confront Israel about its nuclear capability.
''As long as some members of the U N Security Council support this (Israeli) regime with their veto right, there is no guarantee of establishing peace and justice in this region,'' Ahmadinejad told a conference of Asian MPs in Tehran today.
Iran has rejected U N demands to halt enrichment and the U N Security Council is now considering imposing sanctions.
Iran's chief atomic negotiator, Ali Larijani, said passing a sanctions resolution ''means that they (the West) don't want to resolve this issue through talks'', IRNA news agency reported.
Asked if Iran still aimed to start 3,000 centrifuges by the end of the Iranian year in March 2007 -- a step toward planned ''industrial-scale'' enrichment with 54,000, Hosseini said: ''Iran is trying to do so under the supervision of the IAEA.'' The U N watchdog, the Vienna-based International Atomic Energy Agency, makes routine checks of Iran's nuclear sites.
In Vienna, diplomats said the IAEA was unlikely to approve Iran's request for technical help with a heavy-water plant due to fears it could produce plutonium for bombs. The IAEA board has repeatedly asked Iran to ''reconsider'' the project at Arak.
Reuters DKA DB2249