The U.S. military said it has completed its investigation into the February 21 incident in which dozens of Afghan civilians were killed and concluded that more training is needed.
The investigation "cites several shortcomings in training, communication and decision-making, and offered numerous recommendations," a U.S. military release said.
The deaths occurred during a NATO airstrike on a convoy in the Uruzgan province in southern Afghanistan. Up to 23 Afghan civilians were killed and 12 others were wounded, the military said.
At the time of the incident, Gen. Stanley McChrystal, the commander of U.S. forces in Afghanistan, apologized and met with President Harmid Karzai.
McChrystal said the investigation revealed that more training needs to be done with several different combat units working in Afghanistan.
"As partners with the Afghan people in our mission, we must always be honest with ourselves about what we do well and what we can do better," McChrystal said in a statement Friday. "When we make a mistake, we must be forthright and we must do everything in our power to correct that mistake. I know our actions following this thorough investigation will help us to prevent mishaps that result in harm to the people we are sworn to protect."