A US military investigation has uncovered mistakes in air strikes that killed dozens of civilians in western Afghanistan last month.
A US military official has confirmed a report in The New York Times on Wednesday that said the civilian death toll would probably have been reduced if US air crews and ground troops had followed strict rules to prevent civilian casualties.
The incident in early May stoked long-standing tensions between Afghans and foreign troops over civilian casualties.
Afghan officials put the civilian death toll from the air strikes in Farah province as high as 140 while an Afghan human rights watchdog put the total at 97. The rights group said no more than two Taliban fighters were killed.
The US military, by contrast, has said 20 to 35 civilians were among 80 to 95 people killed, most of them Taliban fighters who used the civilians as human shields.
The investigation, whose results have not yet been officially announced, was ordered by General David Petraeus, the head of US Central Command.
The Times, citing an unnamed senior military official, said the investigation had concluded that one US aircraft was cleared to attack Taliban fighters, but circled back and did not reconfirm the target before dropping bombs.
This left open the possibility that the militants had fled or civilians had entered the target area in the intervening few minutes.
A compound where militants were massing for a possible counterattack against US and Afghan troops was struck in violation of rules that required a more imminent threat to justify putting high-density village dwellings at risk, it said.