The Pentagon said on Monday that no US troops or officials would face disciplinary action for a drone strike in Kabul in August that killed 10 Afghan civilians, including seven children.
Spokesman John Kirby said Secretary of Defense Lloyd Austin had received a high-level review of the strike that made no recommendation of accountability.
"He approved their recommendations," Mr Kirby said. "The secretary is not ... calling for additional accountability measures."
"There was not a strong enough case to be made for personal accountability," Mr Kirby added.
The 29 August drone strike took place in the final days of the US-led evacuation of Kabul after the Taliban seized control of the country.
US officials said they had intelligence of a possible Islamic State attack on the evacuation operations at Kabul airport, and launched a missile from a drone at a target that was thought to be a car laden with munitions.
A view of the damage at Zemari Ahmadi's family home after the deadly drone strike. Source: Anadolu
In fact, they struck a family that included an Afghan man who worked for a US aid group and seven children.
In early November, an initial report carried out by the US Air Force inspector general, Lieutenant General Sami Said, called the strike tragic but "an honest mistake".
The review by Central Command head General Kenneth McKenzie Jr and Special Operations Command chief General Richard Clarke made use of Said's report and detailed recommendations on procedures for future drone strikes.
But it made no call for anyone to be punished for the mistake.
"What we saw here was a breakdown in process, in execution and procedural events, not the result of negligence, not the result of misconduct, not the result of poor leadership," Mr Kirby said.
If Austin "believed ... that accountability was warranted, he would certainly support those kinds of efforts," Mr Kirby added.
Compensation payments
The strike killed Zemari Ahmadi, an employee of US-based Nutrition and Education International (NEI), and nine members of his family.
Last month, NEI founder and president Steve Kwon called the Pentagon's investigation into the incident "deeply disappointing and inadequate".
The Pentagon promised to pay compensation and also to help relocate abroad family members and Afghans working for NEI, but that remains stuck on determining just who is qualified, according to officials.
Mr Kirby said they are still discussing arrangements with Mr Kwon.
"We are working very hard with him and his organisation to effect the relocation of the family members," Mr Kirby said.
"We want to make sure we do it in the most safe and responsible way, so that we know it's getting to the right people and only to the right people."
Mr Kirby, meanwhile, refused to comment on a New York Times story on Monday that detailed a secret US military unit that launched drone strikes on Islamic state targets in Syria and had a callous attitude toward civilian deaths.
"We take issues of civilian harm very seriously," Mr Kirby said.
"When we say we take it seriously, we mean it. It doesn't mean we're perfect. It doesn't mean we always get it right," he said.
"And when we don't get it right, we want those mistakes investigated."
