The US military on Friday admitted that a drone strike in Kabul last month killed as many as 10 civilians, including seven children, apologising for the "tragic mistake".
The Pentagon had said the Aug 29 strike targeted an Islamic State suicide bomber who posed an imminent threat to US-led troops at the airport as they completed the last stages of their withdrawal from Afghanistan.
Even as reports of civilian casualties emerged, the top US general had described the attack as "righteous".
According to a Reuters report, the head of US Central Command, Marine Corps General Frank McKenzie, said that at the time he had been confident it averted an imminent threat to the forces at the airport.
"Our investigation now concludes that the strike was a tragic mistake," McKenzie told reporters.
He said he now believed it unlikely that those killed were members of the local Islamic State affiliate, ISIS-Khorasan, or posed a threat to US troops. The Pentagon was considering reparations, McKenzie said.
The killing of civilians, in a strike carried out by a drone based outside Afghanistan, has raised questions about the future of US counter-terrorism strikes in the country, where intelligence gathering has been all but choked off since last month's withdrawal.
And the confirmation of civilian deaths provides further fuel to critics of the chaotic US withdrawal and evacuation of Afghan allies, which has generated the biggest crisis yet for the Biden administration.
In a statement, Defense Secretary Lloyd Austin said the drone strike had killed a Mr. Ahmadi who worked for a non-profit called Nutrition and Education International.
"We now know that there was no connection between Mr. Ahmadi and ISIS-Khorasan, that his activities on that day were completely harmless and not at all related to the imminent threat we believed we faced," Austin said in the statement.
"We apologize, and we will endeavor to learn from this horrible mistake."