The US military has admitted it is partly to blame for a NATO airstrike that killed 24 Pakistani soldiers last month, but refused to offer its apology.
A top US general said on Thursday that an "overarching lack of trust'' between the US and Pakistan, as well as several key communication errors, led to the NATO strikes near the Afghan border.
Brig Gen Stephen Clark, an air force special operations officer who led the investigation into the incident, said "the US forces used the wrong maps, were unaware of Pakistani border post locations and mistakenly provided the wrong location for the troops".
Clark described a confusing series of gaffes rooted in the fact that US and Pakistan do not trust each other enough to provide details about their locations and military operations along the border.
"As a result, US forces on that dark, November 26 night thought they were under attack, believed there were no Pakistani forces in the area, and called in airstrikes on what they thought were enemy insurgents," he said.
A US military statement said its investigation into the incident revealed that there was "no intentional effort to target persons or places known to be part of the Pakistani military".
The Pentagon said that "the US wants to learn from the mistakes and take any corrective measures needed to make sure such mistakes are not repeated".
"For the loss of life and for the lack of proper coordination between US and Pakistani forces that contributed to those losses, we express our deepest regret,'' George Little, Pentagon spokesman, told reporters.
The Pakistani version of events is not included in this report as they refused to co-operate.
A separate NATO investigation, also released on Thursday, found that both the alliance and Pakistani forces made mistakes in the incident, and that forces were unable "to properly coordinate their locations and actions, both before the operation and during the resulting engagement".
The NATO also said that the combined force did not knowingly fire at the Pakistani forces.
"The investigation has substantiated that close air support was employed in self-defence in response to intense, heavy machine gun and mortar fire initiated by what turned out to be Pakistan forces near the border in the vicinity of Salala," a NATO press statement said.
Pakistani officials did not immediately respond to requests for comment on the report.
Pakistan has sought a full apology from President Barack Obama for the strikes, and some officials have alleged it was a deliberate assault on Pakistani troops.
Since the November 26 attack, the Pakistani government has shut down NATO supply routes to Afghanistan and forced the US to shut its operation from Shamsi air base in southwestern Baluchistan province.
The base was used to maintain drones deployed in strikes against armed groups hiding in safe havens in Pakistan's tribal belt on the Afghan frontier.