WASHINGTON (Reuters) -The United States has assessed that Iran manufactured the drone that slammed into a U.S. base in Jordan over the weekend, killing three American soldiers and wounding more than 40, four U.S. officials told Reuters.

Washington has blamed the attack - the first to kill U.S. troops in the Middle East since the start of the Israel-Hamas war in October - on Iran-backed militants, and President Joe Biden’s administration has promised a multi-tiered response that will include strikes.

But it has stopped short of publicly saying where the actual weapon that killed the Americans came from, even as it acknowledged Iran’s ultimate responsibility for funding and even in some cases training the militants responsible.

The officials, who spoke to Reuters on condition of anonymity, did not provide the model of the drone and said analysis was still ongoing.