Watch: Pentagon admits deadly Kabul drone strike was an error
He said: “It was a mistake and I offer my sincere apology. The strike was a tragic mistake. I do feel responsible for it.”
The strike happened on August 29, three days after 13 US troops and more than 160 Afghans were killed in an Islamic State suicide attack at Kabul airport.
For days after the drone strike Pentagon officials had asserted that it had been “righteous”.
They said it was conducted correctly against a Toyota Corolla being driven by a terrorist and carrying explosives that were going to be used to attack the airport.
But news organisations on the ground reported that the driver had been Zemerai Ahmadi, a longtime employee at a US humanitarian organisation.
As he pulled into his drive children came out to see his 11-year-old son park the car, and were hit by a Hellfire missile.
An internal Pentagon review of the strike has now concluded that only civilians were killed in the attack.
Gen. McKenzie said there had been “reasonable certainty” at the time that the car represented a danger, and it was struck “in the earnest belief” there was an imminent threat.
He said: “I am now convinced that as many as 10 civilians, including up to seven children, were tragically killed in that strike.
“Moreover, we now assess that it is unlikely that the vehicle and those who died were associated with Isis-K, or a direct threat to US forces. I am here to set the record straight. “
He said the car had been followed by the US for eight hours, using drones, after it was spotted near a building associated with IS-K.
Intelligence that suggested it was a threat was “clearly wrong”, the general said.
After the strike US officials said a secondary explosion showed there were explosives in the car.
But a review suggested the car was just being used to transport a propane tank.
General Mark Milley, the chairman of the joint chiefs of staff, said: “This is a horrible tragedy of war and it's heart wrenching. We are committed to being fully transparent about this incident.
“In a dynamic high-threat environment, the commanders on the ground had appropriate authority and had reasonable certainty that the target was valid.
“But after deeper post-strike analysis our conclusion is that innocent civilians were killed.”
Lloyd Austin, the US defence secretary, offered his “deepest condolences to surviving family members of those who were killed”.
“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,” he said.
“We apologise, and we will endeavour to learn from this horrible mistake.”
The authority to carry out strikes in Afghanistan – against al-Qaeda or Islamic State – will no longer rest with US commanders in the region, a US defence official told Reuters, adding General Austin himself will have to authorise any future strikes.
Still, the intelligence failure exposed in America's last military strike of its war in Afghanistan raises hard questions about the risks going forward. These include whether the United States can keep track of al-Qaeda and Islamic State threats, and act quickly on any information it gets.
General McKenzie played down the impact the latest civilian casualties would have on future actions in Afghanistan.
“I don't think you should draw any conclusions about our ability to strike in Afghanistan against Isis-K targets in the future based on this particular strike,” he said.Internet Explorer Channel Network