"The enemies, both the USA and the Zionist regime, should know that they will definitely receive a crushing response to what they are doing against Iran, the Iranian nation, and the resistance front," Khamenei said in a speech to students in Tehran.

The supreme leader did not elaborate on the timing of the threatened attack, nor the scope. The US army operates on bases throughout the Middle East, with some troops now manning a Terminal High Altitude Area Defense, or THAAD, battery in Israel, AP reported.

Regional tensions have soared since the start of Israel's war on Gaza drawing in groups from Lebanon, Iraq, Syria and Yemen. The groups have maintained they would halt attacks on Israel as soon as a ceasefire is established in its assault on Gaza.

For nearly a year after Israel's war on Gaza began on October 7, 2023, Hezbollah and Israel had exchanged cross-border fire, before Israel escalated its attacks on Lebanon on September 23.

Khamenei said in earlier remarks that officials would weigh Iran’s response and that Israel’s attack “should not be exaggerated nor downplayed.”

Gen. Mohammad Ali Naini, a spokesman for Iran's paramilitary Revolutionary Guard which controls the ballistic missiles, warned in an interview published by the semiofficial Fars news agency just before Khamenei's remarks were released, that Iran's response "will be wise, powerful and beyond the enemy’s comprehension.”

“The leaders of the Zionist regime should look out from the windows of their bedrooms and protect their criminal pilots within their small territory,” he warned.

Iran has launched two major retaliatory attacks on Israel, in April and October.

On October 26, Israel conducted air strikes on military sites in Iran in response to Tehran's October 1 attack on Israel, itself retaliation for the killing of Hezbollah leader Hassan Nasrallah and a Revolutionary Guards commander.

At least four soldiers were killed in the attack which Iran said caused "limited damage" to a few radar systems. Iranian media said a civilian was also killed.

In his speech, Khamenei paid tribute to the slain soldiers, saying their efforts in confronting Israel "will not be forgotten," according to AFP.

The United States announced Friday the deployment of additional military assets to the Middle East, including ballistic missile defence destroyers and long-range B-52 bomber aircraft, serving as a warning to Iran as it and Israel trade tit-for-tat strikes.

Khamenei said Iran was "certainly doing everything that should be done to prepare the Iranian nation, whether in terms of military, in terms of weapons, or in terms of political work."

The supreme leader met with university students to mark Students Day, which commemorates a November 4, 1978, incident in which Iranian soldiers opened fire on students protesting the rule of the shah at Tehran University. The shooting killed and wounded several students and further escalated the tensions consuming Iran at the time that eventually led to the shah fleeing the country and the 1979 Islamic Revolution.