Iran's supreme leader on Thursday warned Israel and the United States that Tehran's response will be tough should its archenemies choose a military strike against Iran over the country's controversial nuclear program.

"Anybody who takes up the idea of an attack on Iran, should get ready to receive a strong slap and an ironfist" by the Iranian armed forces, said Ayatollah Ali Khamenei.

Khamenei spoke two days after the U.N. atomic agency released a report that for the first time said Iran is suspected of conducting secret experiments whose sole purpose is the development of nuclear arms.

The report was the International Atomic Energy Agency's most unequivocal yet in suggesting Iran is using the cover of a peaceful nuclear program to produce atomic weaponry. Iran insists it is pursuing nuclear energy for peaceful purposes.

On Wednesday, Iranian President Mahmoud Ahmadinejad slammed the IAEA report, defiantly saying Tehran would not retreat "an iota" from its nuclear program, which includes enriching uranium — a potential path to making a nuclear bomb.

The U.S. and its allies are concerned that a nuclear-armed Iran could touch off a nuclear arms race among rival states, including Saudi Arabia, and directly threaten Israel. Four rounds of U.N. sanctions so far have not succeeded in getting Tehran to halt its enrichment program.

Israel sees Iran as an existential threat, citing Ahmadinejad's calls for Israel's destruction and Iran's support for Arab militant groups. Ahead of the IAEA report's release on Tuesday, Israeli Defense Minister Ehud Barak had said that without effective sanctions, Israel would not take any option "off the table," a reference to possible military action.

Khamenei's rhetoric Thursday was just as defiant — an indication that Iran is seriously viewing comments by the West in the aftermath of the IAEA report and in particular, by Israel on a possible military strike against its nuclear facilities.

"The enemies, particularly the United States and its pawns and the Zionist regime, should know that the Iranian nation does not seek to invade any country or nation," Khamenei said, addressing officers at a military academy in Tehran.

"But Iran will strongly respond to any invasion or attack with such power and in a way that the aggressors and invaders will be smashed from the inside," said Khamenei, who has final say on all state matters in Iran. His remarks were quoted by state radio.

"The Iranian nation is not a nation that only sits and watches threats coming from straw powers, which are internally eaten by worms," he added.