"If maniacs in Washington or Tel Aviv seek to take action, the Iranian nation will slap them so hard they will not get off the floor," hardline cleric Ahmad Khatami said in a Friday prayer sermon carried live on state radio.
The Pentagon on Wednesday denied reports of new plans for military options against Iran, which is accused by the United States of seeking nuclear weapons, sponsoring terrorism and meddling in Iraq.
Iran vehemently denies all the charges.
However, Washington has never ruled out a military option in a bid to thwart Iran's nuclear drive, which Tehran insists is solely aimed at peaceful energy production.
The cleric said the fact that the United States had not yet attacked Iran was because it "has not been possible, not that it did not want to."
"Death be upon" Israel for "celebrating the killing of innocent people" in the Gaza Strip, Khatami also said. Iran does not recognise Israel, and President Mahmoud Ahmadinejad has called for the annihilation of the Jewish State.
"Israel should know that these pressures will pave the way for another Intifada which will turn the Israelis' day into night," Khatami said.
Israel, the Middle East's sole if undeclared nuclear power, accuses Iran of seeking atomic weapons and has urged tougher punitive measures against Tehran, which is already under three sets of UN Security Council sanctions for its refusal to halt uranium enrichment.
Khatami also took a swipe at US Democrat presidential hopeful Hillary Clinton for her threat to "totally obliterate" Iran if it launched a nuclear attack on Israel.
"Shame on you that your presidents should be weak-willed servants of Israel," he said.
