American and Pakistani forces both made a series of mistakes that led to "tragic" US air strikes which killed 24 Pakistan soldiers last month, reflecting deep mutual mistrust between the two nations, said a US-led probe released on Thursday.
The results of the joint US-Nato investigation portrayed a disastrous spate of errors and botched communication in the November 25-26 incident, in which both sides failed to tell the other information about their operational plans or the location of troops, officers said.
The probe found "inadequate coordination by US and Pakistani military officers" and acknowledged the Americans had relayed "incorrect mapping information" to a Pakistani liaison officer that gave the wrong location for Pakistani troops at border outposts, the Pentagon said in a statement.
US aircraft carried out three strikes after American and Afghan commandos staging a night raid on a village near the Pakistani border came under heavy machine-gun and mortar fire, said Brigadier General Stephen Clark, who led the probe.
The US side did not tell the Pakistanis in advance about the raid near the border, and the Pakistanis had never notified Nato of new border posts in the area, he said.
The incident triggered outrage in Pakistan and aggravated tensions in an already shaky relationship, prompting Islamabad to block crucial Nato supply convoys to Afghanistan.
"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," the US statement said, stopping short of an apology.
By placing blame on both US and Pakistani forces, the probe's findings could further anger Islamabad, where officials have insisted their troops did nothing wrong, and did not fire first.
Pentagon press secretary George Little told reporters the United States would be offering payments to the families of the victims and that top officers had briefed Pakistani army chief General Ashfaq Kayani on the probe's findings.
The Nato alliance agreed with the probe's findings and said "a series of mistakes were made on both sides in failing to properly coordinate their locations and actions, both before the operation and during the resulting engagement."
According to the investigation, US and Afghan forces on the ground had come under direct machine-gun and mortar fire from the border and first called in F-15s and an AC-130 gunship in a "show of force," said Clark, speaking to reporters by phone from Hurlburt Field, Florida.
Despite warplanes streaking overhead that signaled the presence of Nato forces, the hostile fire persisted, Clark said.
Before requesting air strikes, the ground commander first asked his superiors to check if there were any Pakistani forces in the area, and he was told there were not, the general said.
An AC-130 gunship attacked the source of the hostile fire in the first air strike, then two Apache attack helicopters joined the fight in a second strike before midnight, he said.
At about the same time, Pakistani liaison officers phoned the Nato-led coalition "to say that their forces are under fire," Clark said.
But the Pakistanis were unwilling to give the precise location of their troops.
"When asked, the general answer back was, 'Well, you know where it is because you're shooting at them,' rather than giving a position," Clark said.
Moreover, a coalition soldier at a border coordination center was told not to give the precise map coordinates of US troops to his Pakistani counterpart, and instead described the area where the firefight was taking place, he said.
But that soldier had the wrong overlay on his computer and passed on inaccurate information to the Pakistani officer, referring to an area 14 kilometers (nine miles) away from the firefight, Clark said.
Finally, after a third air strike at a second location to the north, Nato confirmed the presence of Pakistani forces in the area and ordered a halt to attacks, he said.
The episode reflected "an over-arching lack of trust between the two sides as far as giving out specifics," Clark said.
Officers in the International Security Assistance Force (ISAF) view Pakistan as reluctant to disclose all their border posts while ISAF has the impression that when they have shared details that some operations have been "compromised," he said.
The investigation involved dozens of interviews but lacked Pakistan's perspective as Islamabad had refused to take part in the probe, he said.
"If we're trying to find out what occurred in total, that's a significant element there that is missing, because there's always two sides to a particular event," he said.
The general said it was up to senior commanders to decide if any officer involved in the incident would be disciplined.