Retired Maj. Gen. James A. "Spider" Marks made the remark as Staff Sergeant Robert Bales stands accused of carrying out the massacre in three different villages in the southern district of Panjwaii, on March 11.
According to a fact-finding mission set up by the Afghan parliament, at least 20 US soldiers were involved in the massacre of 16 civilians, including nine children.
However, US officials still insist that only one soldier was responsible for the killings. Bales was flown out of Afghanistan last week.
The Afghan parliamentary mission investigating the rampage says two women were also raped during the deadly incident.
Relations between the two countries have plummeted to a new low as a result of the massacre of Afghan civilians.
The US-led invasion of Afghanistan was launched in 2001 under the pretext of removing the Taliban from power; however, insecurity has been growing across the country, despite the presence of tens of thousands of US-led forces there.