A US air strike that destroyed a hospital run by Medecins Sans Frontieres in the northern Afghan city of Kunduz last month was the result of human errors, failures in procedure and technical malfunctions", the New York Times reports.
The newspaper cites an unnamed senior US Defense Department official, who it says was briefed on an internal investigation.
The Pentagon says the findings of the military investigation into the October 3 attack, which left 30 people dead and at least 37 wounded, will be made public on Wednesday.
The medical charity condemned the strike as a war crime.
"It's a combination of factors," the Times quoted an unnamed senior Defense Department official as saying, describing the findings in what it said was a 3,000-page investigative file.
Two other military officials said the Air Force AC130 gunship that attacked the hospital was intended to target a different compound several hundred metres away that was believed to be a Taliban base of operations, the paper reported.
The "crew had been unable to rely on the aircraft's instruments to find the target.
Instead, they relied on verbal descriptions of the location that were being relayed by troops on the ground, a mix of American and Afghan Special Forces," the Times said.
President Barack Obama apologised for the bombing of the hospital.
MSF, or Doctors Without Borders, has demanded an international humanitarian commission to investigate the attack.
