In a statement issued later on Thursday, the Pentagon said “inadequate coordination by US and Pakistani military officers” and “our reliance on incorrect mapping information ... contributed to this tragic result.”

The WSJ said the investigation, due to be presented to US defense officials on Friday, acknowledges significant US responsibility for the Nov. 26 air strike that deepened mistrust between the United States and Pakistan. It cited unidentified US officials familiar with the report.

The Pentagon statement expressed “deepest regret” for the loss of life and the lack of coordination that contributed to it. However, it also said US forces cannot operate effectively in Pakistani border areas “without addressing the fundamental trust still lacking between us.”

The uneasy allies faced a series of crises in the past year, including the US raid that killed Al-Qaeda leader Osama Bin Laden on Pakistani soil in May, the closure of NATO supply routes through Pakistan, and the arrest of a CIA contractor.

The US military report supports some main elements in Pakistan’s version of events and conflicts with early US accounts that said Pakistanis gave an all-clear before what would become the most deadly friendly fire accident of the war in Afghanistan, the newspaper said.

“The overarching issue that surrounds this incident is a lack of trust” between the United States and Pakistan that led to the incident, the Journal quoted a military official as saying.

The air strike incensed the Pakistanis, who demanded that the United States leave the Shamsi Air Base within 15 days and blocked ground supply routes through Pakistan to US forces in Afghanistan. They also want a formal US apology.

According to the newspaper, the US report says a US-Afghan commando team came under attack from positions along a ridgeline, after which an F-15 fighter jet and AC-130 gunship launched warning flares toward the positions high above the commandos.

Forces on the ground asked NATO for a report on the area, the Journal reported, and were told in a radio transmission: “We are not tracking any pak mil (Pakistan military) in the area.”

The ground forces interpreted that to mean there was no Pakistani military there, a military official familiar with the report told the Journal.

A second mistake involved inaccurate data provided by the US forces to the Pakistani military at a border coordination center, the report said.

However US military officials said Pakistani forces should have realized they were not firing on insurgents because of the fighter jets and gunships, the newspaper reported.

“It’s hard to mistake these units for insurgents,” a US official told the Journal. “One of the gaps in this investigation is we don’t know why they came under fire by the Pakistani military.”