"At times the officials of the Zionist regime (Israel) threaten to launch a military invasion but they themselves know that if they make the slightest mistake the Islamic Republic will raze Tel Aviv and Haifa to the ground," Ayatollah Ali Khamenei said in an address to mark the Iranian new year.
Israel has threatened military action against Iran unless it abandons nuclear activities which the West suspects are intended to develop nuclear weapons. Tehran denies this, saying it wants nuclear energy only for civilian purposes.
Khamenei said Iran's struggles over the past year against international sanctions imposed over its disputed nuclear programme resembled a battle and its enemies had confessed to trying to "cripple the Iranian nation".
"What happened last year we need to learn a lesson," he said, alluding to what he described as Iran's significant scientific and military advances. "This vibrant nation will never be brought to its knees."
Talks between Iran and six world powers - the United States, China, Russia, Britain, France and Germany - are to resume early next month in a further attempt to strike a deal on Iranian nuclear aspirations.