The United States had no involvement in an Israeli airstrike on Iran's consular annex building in the Syrian capital Damascus and was not informed about it in advance, officials have said.
Tehran has vowed to retaliate for the strike, which killed more than a dozen people - including senior members of the Revolutionary Guards - while Israel has so far declined to comment.
"We had nothing to do with the strike in Damascus, we weren't involved in any way whatsoever," National Security Council spokesman John Kirby told a briefing.
Mr Kirby dismissed as "nonsense" comments by Iran's foreign minister that the United States, Israel's main backer, bore responsibility for the attack.
Deputy Pentagon Press Secretary Sabrina Singh also said Washington's forces played no role in the strike, and that the United States conveyed this to Tehran through private channels.
"We were not notified by the Israelis about their strike or the intended target of their strike in Damascus," Ms Singh told journalists. "We've made it very clear in private channels to Iran that we were not responsible for the strike."
Iranian state media said 13 people were killed in yesterday's strike - seven members of Tehran's Revolutionary Guards and six Syrian nationals.
The Guards said the dead included two top commanders: Brigadier General Mohammad Reza Zahedi and Brigadier General Mohammad Hadi Haji Rahimi.
Ms Singh said Washington assesses that senior Revolutionary Guards leaders were killed, but has not been able to independently confirm their identities.
Israel declined to comment on the strike, which fuelled Middle East tensions already enflamed by the war in Gaza between Israel and Iran ally Hamas.
Iran's supreme leader Ayatollah Ali Khamenei vowed that Israel would be punished.
"The evil Zionist regime will be punished at the hands of our brave men. We will make them regret this crime and the other ones," he said in a message published on his official website.
President Ebrahim Raisi condemned the attack as a "clear violation of international regulations" which "will not go unanswered".
"After repeated defeats and failures against the faith and will of the Resistance Front fighters, the Zionist regime has put blind assassinations on its agenda in the struggle to save itself," Mr Raisi said on his office's website.
Iran's ambassador to Syria, Hossein Akbari, told Iranian state TV that the attack "was carried out by F-35 fighter jets" which fired six missiles at the building.
Only the gate of the building was left standing after the attack, with a sign reading "the consular section of the embassy of Iran".
Earlier, Iran's foreign minister said Israel's main backer the United States also bore responsibility for the strike.
Amir-Abdollahian said on X that the ministry had summoned a diplomat from the Swiss embassy, which looks after US interests in Iran, to hear its protest.
"An important message was sent to the American government as the supporter of the Zionist regime. America must be held accountable," he said in the post.
Iran's mission to the United Nations warned the strike could "potentially ignite more conflict involving other nations" and called on the Security Council "to condemn this unjustified criminal act."
Iran's allies around the region and beyond voiced support for its position.
"China condemns the attack," foreign ministry spokesperson Wang Wenbin said, adding "the security of diplomatic institutions cannot be violated, and Syria's sovereignty, independence and territorial integrity should be respected".
The Iraqi foreign ministry condemned the attack as a "flagrant violation of international law" and warned of "more chaos and instability" in the region.
Lebanon's Iran-backed Hezbollah group warned Israel would pay for killing Guards commanders. "This crime will not pass without the enemy receiving punishment and revenge," Hezbollah said in a statement.
Russia blamed the Israeli air force for the "unacceptable attack against the Iranian consular mission in Syria".
Palestinian militant group Hamas condemned the strike, which it described as a "dangerous escalation".
The Gaza war erupted with Hamas's unprecedented 7 October attack that resulted in about 1,160 deaths in Israel, mostly civilians, according to an AFP tally of Israeli official figures.
Israel's retaliatory offensive against Hamas has killed nearly 33,000 people in Gaza, mostly women and children, according to the Hamas-run territory's health ministry.
Iran-backed groups in Iraq, Lebanon, Syria, and Yemen have since carried out a series of attacks on Israeli and Western targets.
Israel operating 'all over Middle East' against foes, defence chief says
Israel is operating all over the Middle East to exact a price from those who threaten it, the country's defence minister said, though he did not refer directly to yesterday's attack in Damascus.
"We are currently in a multi-front war - we see evidence of this every day, including over the last few days," Defence Minister Yoav Gallant told a parliamentary committee, according to a statement from his office.
"We operate everywhere, every day, in order to prevent our enemies from gaining strength and in order to make it clear to anyone who threatens us - all over the Middle East - that the price for such action will be a big one."
