"We must work to improve the level of trust between our two countries," the report concluded. "We cannot operate effectively on the border -- or in other parts of our relationship -- without addressing the fundamental trust still lacking between us. We earnestly hope the Pakistani military will join us in bridging that gap."
The report suggested there were mistakes on both sides with the incident Nov. 26, beginning when soldiers in a Pakistani border outpost fired on a joint U.S.-Afghan contingent.
On the other side, Brig. Gen. Stephen Clark said a message that NATO was "tracking no Pak mil in the area" was heard as a definitive statement that there were no Pakistanis in the area. Later, Pakistan was given the wrong coordinates for the firefight.
Pakistan closed NATO supply routes after the incident, the deadliest involving friendly fire in the Afghan war. The government has demanded an apology for the deaths.
There was no apology Thursday. Pentagon Press Secretary George Little instead expressed "deep regret."
"We further express sincere condolences to the Pakistani people, to the Pakistani government and most importantly to the families of the Pakistani soldiers who were killed or wounded," he said.
Pakistan reportedly disputes the report's contention that its troops fired first.
"The findings are strange, and contradict what we have communicated so far to the Americans. This report is not good news," an intelligence officer told CNN.
2014: The Year in Fashion [PHOTOS]
Cyclist struck and dragged underneath car