US President Joe Biden has pledged "ironclad" US support to Israel amid fears that Tehran could retaliate after an attack that killed senior Iranians, according to the BBC.
Biden warned that Iran is threatening to launch a "major attack" after Israel struck the Iranian consulate in Syria 10 days ago.
"We will do everything we can to protect Israel's security," he added.
Earlier on Wednesday, the Iranian leader said the Israeli attack on Damascus was tantamount to an attack on Iran itself.
"When they attacked our consulate area, it was like they attacked our territory," Ayatollah Ali Khamenei said in a speech.
"The bad regime must be punished and it will be punished," he added.
It is not yet clear what form any retaliatory attack would take.
If Iran strikes Israel directly, it would risk an even greater escalation of the conflict, while analysts said Iran lacks the military capability for a significant confrontation.
A possible alternative is an attack via an Iranian proxy such as Hezbollah, which often carries out smaller attacks on Israel from neighboring Lebanon.
On Sunday, an Iranian official warned that Israel's embassies were no longer secure, suggesting the consulate building could be a possible target.
Experts have also suggested that Iran could target Israel with a cyber attack.
In the April 1 attack on the Iranian consulate building, 13 people were killed, including senior Iranian military leaders.
Israel has not claimed responsibility for the attack, but is widely believed to be behind it.
American and Israeli forces in the region have been put on high alert these days.
Biden's statement came as he spoke to reporters Wednesday at the White House alongside Japanese Prime Minister Fumio Kishida.
"As I told Prime Minister Netanyahu, our commitment to the security of Israel against these threats from Iran and its proxies is 'ironclad' - let me say that again, ironclad," Biden said.
His reaction comes a day after Biden, in an interview, called for a cease-fire in Gaza, adding that he disagreed with Netanyahu's war strategy.
"I think what he is doing is a mistake. I don't agree with his approach", he said in an interview for "Univision".
According to the Hamas-run Ministry of Health in Gaza, more than 33,000 people – mostly women and children – have been killed in the Israeli incursion.
The conflict was sparked by Hamas killing more than 1,200 people in Israel and taking 253 hostages in the October attack.