Iran is set to hit Israel with a "definitive and painful" response to the Jewish state's strikes on October 26.
In the latest twist in an increasingly bitter campaign between the two countries, a high-ranking source said that Israel's attacks will be met with retaliation in just a few days' time.
The source, whom US outlet CNN described as being "familiar with Iran's deliberations", told the broadcaster that Iran's retaliation would come before the American presidential election on November 5.
"The response of the Islamic Republic of Iran to the aggression of the Zionist regime will be definitive and painful," they said.
Ayatollah Ali Khamenei said Israel's strikes should 'neither be exaggerated nor downplayed' in a rather more measured statement
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The source's tone marks a clear ramping-up in rhetoric from that of Iran's supreme leader.
In his initial response to the Israeli bombardment on Saturday, Ayatollah Ali Khamenei said the strikes should "neither be exaggerated nor downplayed".
But the new threats have prompted condemnations from the US.
White House spokeswoman Karine Jean-Pierre said bluntly: "Iran should not respond to Israel's retaliation."
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Iran had rained down missiles on Israel on October 1 - which was met with Israel's own "precise strikes"
REUTERS
But she added: "If Iran does choose to respond... the US will be standing by to assist Israel in its defence."
While US State Department spokesman Matthew Miller refused to comment on what Iran "may or may not do," he said the US believes "they should not respond".
Miller would also not be drawn on whether the Islamic Republic had indicated to the US that it intended to respond before November 5.
He told reporters on Wednesday: "I'm not going to talk about communications between our two governments, real or imagined.
The US will be 'standing by to assist Israel in its defence', the White House said
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"But as we have made clear publicly, and I can tell you that Iran knows this message quite clearly, they should not continue to escalate this conflict."
Iran itself had rained down missiles over Israeli cities and military targets on October 1 - but was then rocked 25 days later by a series of "precise strikes" on military technology targets.
And its terror group proxy Hezbollah has vowed to continue on the warpath against Israel.
In his first remarks since becoming head of the group yesterday, the paramilitary's new leader Naim Qassem said: "We will continue our war plan within the outlined political frameworks... We will remain on the path of war," adding that he planned to follow the agenda set by his dead predecessor, Hassan Nasrallah.
