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.

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," 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 the Monday 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.

Singh said Washington assesses that senior Revolutionary Guards leaders were killed, but has not been able to independently confirm their identities.