Iran will target "32 US bases and the heart of Israel" if it is attacked, the Fars news agency quoted an aide to supreme leader Ayatollah Ali Khamenei as saying on Saturday.
"If America and Israel shoot any bullets and missiles against our country, Iranian armed forces will target the heart of Israel and 32 US bases in the region before the dust from this attack has settled," Mojtaba Zolnoor said.
Zolnoor is Khamenei's deputy representative for the elite Revolutionary Guards, the force which controls Iran's more potent weaponry, particularly its longer-range missiles capable of striking Israel and US bases in the Gulf.
The United States and its top regional ally Israel have never ruled out attacking Iran over its nuclear drive, which the West fears could be aimed at making nuclear weapons.
There has been concern an attack against Iran could be imminent after it emerged Israel had carried out maneuvers in Greece that were effectively practice runs force a potential strike agains Iranian nuclear facilities.
Government spokesman Gholam Hossein Elham on Saturday dismissed speculation that Iran risked being attacked by the United States, saying that a military strike would be "craziness."
The Islamic republic has repeatedly warned of a crushing response to any aggression against its soil.
Iran rejects the Western accusations and insists its nuclear programme is aimed solely at generating energy for a growing population whose fossil fuel reserves will eventually run out.
Tensions over the nuclear standoff have surged again in recent days after Iran test-fired a broadside of missiles -- including one it says brings Israel within range -- in war games that provoked international concern.