A US investigation today found that both American and Pakistani forces were to blame for an incident that killed 24 Pakistani troops in a remote area along the Afghanistan-Pakistan border last month, inflaming already strained bilateral ties.
The US military blamed Pakistani soldiers for firing at Nato forces across the border in Afghanistan, triggering the incident, which took place overnight between 25-26 November.
But the US investigation also conceded a critical error by US troops - telling Pakistan the cross-border shooting was taking place about 9 miles away, due to mapping error. Pakistan responded by saying it had no troops there.
"Inadequate coordination by US and Pakistani military officers operating ... resulted in a misunderstanding about the true location of Pakistani military units," Pentagon spokesman George Little said.
"This, coupled with other gaps in information about the activities and placement of units from both sides, contributed to the tragic result," he said.
The death of the Pakistani soldiers dug in along the mountainous, remote border area, along with the initial Nato response, has incensed Pakistanis and marked yet another setback in the Obama administration's efforts to improve chronically troubled ties with an uneasy ally against militants.
The incident prompted Pakistan to shut down ground routes used to supply US forces in Afghanistan and to demand that the United States vacate an air base used to launch drone flights within 15 days. Suggesting the strike may have been intentional, Pakistan has angrily waited for a formal US apology.
Little expressed regret over the deaths.
Brigadier General Stephen Clark, who headed the military US investigation, said US aircraft including fighter jets and attack helicopters came under fire late on the night of 25 November as it approached an Afghan village right over the Pakistani border for a routine mission.
After the Nato forces began receiving mortar and machine gun fire from a ridge area, US officials and a Pakistani border liaison officer embedded with Nato forces concluded - acting on an erroneous analysis of where the firefight was taking place - that no Pakistani military involved so they returned fire.
Part of the problem, Clark said, were instructions to US soldiers not to directly share details of their geographic assessments with their Pakistani liaison officers - a symptom of what he called "an overarching lack of trust" on both sides.
When US forces sought a precise location of allied soldiers from a commander in Pakistan, the exchange further illustrated mutual wariness, Clark said.
"When asked, the (Pakistani) general answer back was, 'Well, you know where it is because you're shooting at them,' rather than giving a position."
In a statement released today, Nato said that a "combined international and Afghan force was initially fired upon by unidentified forces, then believed not to be Pakistani military, and legitimately responded in self-defence."
US officials said they would offer to brief the Pakistani government on the findings of the investigation and were ready to pay compensation to victims' families.
US officials said General Martin Dempsey, chairman of the US Joint Chiefs of Staff, had a "professional and cordial" conversation with General Ashfaq Kayani, the head of the Pakistani military, about the report last night.
Pakistan refused to take part in the investigation, which Clark said had hindered a deeper understanding of the incident.
The friendly fire incident is only the latest of a series of bilateral crises in the past year, including the US raid that killed al Qa'ida leader Osama bin Laden on Pakistani soil in May and the arrest in Pakistan of a CIA contractor.
It is unlikely the conclusions of the report will placate Pakistani military leadership in the charged climate following the incident.
Yet US officials said they would now focus on improving communication with Pakistan and avoiding a repeat of such bloodshed.
"We cannot operate effectively on the border, or in other parts of our relationship, without addressing the fundamental trust still lacking between us," Little said.
"We earnestly hope the Pakistani military will join us in bridging that gap."