A Katyusha rocket was fired at the US embassy compound in Baghdad on Wednesday, setting off sirens in the area.
The attack was first reported by Iraqi news outlets just before midnight local time.
The reports said the rocket was launched from nearby Al Shaab International Stadium in Baghdad. Iraqi military sources confirmed the attack.
There were no reports of casualties and earlier footage suggested the rocket landed in the Green Zone area but outside the embassy compound.
It landed near the US-Iraqi joint operations centre in the Green Zone, Al Hadath news channel reported.
The attack comes on the sixth anniversary of the ISIS takeover of Mosul in Iraq, and on the eve of US-Iraqi strategic dialogue set to begin on Thursday.
The event will be happening online between officials in Baghdad and Washington.
No group claimed responsibility for the attack but similar attacks using Katyusha rockets in the past have been carried out by pro-Iran militias in the country.
The head of US Central Command, Gen Kenneth McKenzie, told the Middle East Institute on Wednesday that the US-Iran standoff in Iraq was a "contested deterrence" since the US killed Iran's Revolutionary Guard leader Qassem Suleimani in January.