The US is on high alert over the possibility of significant retaliation from Iran following a deadly airstrike in Syria, according to American officials.

It comes after the commander of Iran’s Revolutionary Guard vowed “our brave men will punish the Zionist regime” after an airstrike on a building next to Iran’s embassy in Damascus killed seven members of the group on Monday.

Tehran has blamed Israel for the strike, though the Israeli military has refused to comment either to confirm or deny involvement.

US officials have said they are now concerned that Iran may be planning to hit targets inside Israel in retaliation, sparking another expansion of hostilities in the Middle East.

Speaking to NBC News – the US partner of Sky News – on condition of anonymity, two officials said any retaliation inside Israel was likely to focus on military or intelligence targets rather than civilians.

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One official said that Washington received a message from Iran following the strike, and “made clear” to Tehran in response that “we were not behind the strike”.

“We also warned Iran to not use the strike as a pretext to further escalate in the region or attack US facilities or personnel,” they added.

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The two officials also told NBC News that Iran could carry out an attack using a swarm of drones or land-attack cruise missiles against an Israeli diplomatic or consular facility.

Another official separately told CNN that “we’re definitely at a high state of vigilance” over the threat of retaliation.

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Iran said the strike targeted a consular building and therefore was considered an attack on Iran itself.

It said seven Iranian military advisers died in the strike, including Mohammad Reza Zahedi, a senior commander in its Quds Force, which is an elite foreign espionage and paramilitary arm.

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On Thursday, the White House said US President Joe Biden and Israeli Prime Minister Benjamin Netanyahu discussed the threat from Iran in a phone call.

“Our teams have been in regular and continuous contact since then. The United States fully supports the defence of Israel against threats from Iran,” a senior Biden administration official said.

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Mohammad Jamshidi, a top aide to Iranian President Ebrahim Raisi, said on Friday that Tehran sent a message warning the US not to get involved in the fight between Israel and Iran.

He wrote on X that, in response, the US asked Iran not to target American facilities.

However, a US spokesperson for the National Security Council said the reports were “simply wrong” and “Iranian spin”.

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