White House national security spokesman John Kirby dismissed as "nonsense" Iranian charges of US responsibility for Monday's bombing, and he warned that Washington would respond to any retaliatory attacks.
"Let me make it clear. We had nothing to do with the strike in Damascus," he told a briefing. "We weren't involved in any way."
In response to US support for Israel, Iran-backed militias have targeted US military bases in Iraq, Syria and Jordan, although there have been no such attacks since early February following US retaliatory strikes.
"We always take our force protection very seriously, to protect our troops, our facilities in Iraq and Syria," said Kirby. "We will do whatever we need to do to protect those troops."
Pentagon spokesperson Sabrina Singh said Israel provided no advance warning of the strike on the Iranian mission in the Syrian capital.
"We were not notified by the Israelis about their strike or the intended target of their strike in Damascus," Singh told a briefing, adding that Iran had been privately told the US was not behind the strike.
Shortly before the attack, Israel notified the United States that it would be operating in Syria, but used vague language that did not identify a target, two officials saidon condition of anonymity.