WASH INGTON - United States forces failed to follow procedures in carrying out deadly air strikes last month in western Afghanistan that killed dozens of civilians, the Pentagon said. Pentagon spokesman Geoff Morrell said the military's internal investigation into the American assault on the village of Granai identified several problems, most notably that a B-1 bomber lost sight of one of its targets on the ground before dropping its bombs. He said it wasn't clear whether the B-1 crew's loss of positive identification of its target resulted in civilian deaths, but that military investigators "did note that as one of the problems associated with how this all took place." Washington and Kabul have feuded publicly for weeks over the airstrikes, with Afghan officials alleging that US forces killed 140 civilians. US officials have consistently put the number of civilian casualties at around 30, with at least 60 Taliban militants killed. "There were some problems with some tactics, techniques and procedures, the way in which close air support was supposed to have been executed in this case," Morrell told reporters on Monday. The investigation results, which included video taken by pilots involved in the airstrikes, were presented to Defence Secretary Robert Gates on Monday. Officials at the US Central Command said an unclassified version of the report would be released in coming days. Morrell said it was possible US forces could be disciplined for their roles in the strikes, but that he didn't have any sense "that charges are imminent or warranted in this case." He declined to disclose the report's final estimate of how many civilians died, but said "they were greatly outnumbered by the Taliban killed in this incident." Airstrikes have triggered strong anti-American sentiment in Afghanistan, after hundreds of civilians were killed in US raids in recent months. The Obama administration's nominee to run the war, Lt-Gen Stanley McChrystal, told a Senate panel earlier this month that he would review US operating procedures to look for new ways to minimize civilian casualties. "I believe the perception caused by civilian casualties is one of the most dangerous things we face in Afghanistan ," he said. The American assault on the village of Granai began when Taliban militants reportedly beheaded three Afghan officials and then ambushed the Afghan and US forces that responded to the killings. Marine units on the ground radioed for help, and American F-18 fighters, and at least one B-1 bomber, struck targets in the village.