WASHINGTON (AP) — The Pentagon has retreated from its defense of a drone strike that killed multiple civilians in Afghanistan last month, announcing that a review revealed that only civilians were killed in the attack, not an Islamic State extremist as first believed.

“The strike was a tragic mistake," Marine Gen. Frank McKenzie, head of U.S. Central Command, told a Pentagon news conference Friday.

McKenzie apologized for the error and said the United States is considering making reparation payments to the family of the victims. He said the decision to strike a white Toyota Corolla sedan, after having tracked it for about eight hours, was made in an “earnest belief" — based on a standard of “reasonable certainty" — that it posed an imminent threat to American forces at Kabul airport. The car was believed to have been carrying explosives in its trunk, he said.

For days after the Aug. 29 strike, Pentagon officials asserted that it had been conducted correctly, despite 10 civilians being killed, including seven children. News organizations later raised doubts about that version of events, reporting that the driver of the targeted vehicle was a longtime employee at an American humanitarian organization and citing an absence of evidence to support the Pentagon's assertion that the vehicle contained explosives.

The airstrike was the last of a U.S. war that ended as it had begun in 2001 — with the Taliban in power in Kabul. The speed with which the Taliban overran the country took the U.S. government by surprise and forced it to send several thousand troops to the Kabul airport for a hurried evacuation of Americans, Afghans and others. The evacuation, which began Aug. 14, unfolded under a near-constant threat of attack by the Islamic State group’s Afghanistan affiliate.

McKenzie, who oversaw U.S. military operations in Afghanistan, including a final evacuation of U.S. forces and more than 120,000 civilians from Kabul airport, expressed his condolences to the family and friends of those killed.

“I am now convinced that as many as 10 civilians, including up to seven children, were tragically killed in that strike," McKenzie said. “Moreover, we now assess that it is unlikely that the vehicle and those who died were associated with ISIS-K or were a direct threat to U.S. forces," he added, referring to the Islamic State group's Afghanistan affiliate.

Prior to the strike, U.S. intelligence had indicated a likelihood that a white Toyota Corolla would be used in an attack against U.S. forces, McKenzie said. On the morning of Aug. 29, such a vehicle was detected at a compound in Kabul that U.S. intelligence in the preceding 48 hours had determined was used by the Islamic State group to plan and facilitate attacks. The vehicle was tracked by U.S. drone aircraft from that compound to numerous other locations in the city before the decision was made to attack it at a point just a couple of miles from Kabul airport, McKenzie said.

“Clearly our intelligence was wrong on this particular white Toyota Corolla," he said.

Defense Secretary Lloyd Austin, in a written statement, apologized for what he called “a horrible mistake.”

“We now know that there was no connection" between the driver of the vehicle and the Islamic State group, and that the driver's activities that day were “completely harmless and not at all related to the imminent threat we believed we faced," Austin said.

Gen. Mark Milley, chairman of the Joint Chiefs of Staff, told reporters two days after the attack that it appeared to have been a “righteous” strike and that at least one of the people killed was a “facilitator” for the Islamic State group’s Afghanistan affiliate, which had killed 169 Afghan civilians and 13 American service members in a suicide bombing on Aug. 26 at the Kabul airport.

After McKenzie's remarks on Friday, Milley expressed regret.

“This is a horrible tragedy of war and it’s heart wrenching," Milley told reporters traveling with him in Europe. “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," Milley added.