The NATO- led International Security Assistance Force (ISAF) apologized on Monday for an air strike that killed about 14 civilians in the south-west of the country.
Afghan President Hamid Karzai earlier condemned the strike in Helmand, BBC reported. He said Kabul had repeatedly asked the US to stop raids and this was his last warning.
The White House said it has taken Karzai's concerns very seriously.
Gen David Petraeus, Lt Gen David Rodriguez and Marine Maj Gen John Toolan issued a joint statement on Monday, which said that the air strike was carried out after a US Marine was killed and five insurgent took shelter in a compound in Nawzad district.
The generals admitted in the statement that nine civilians who were in the building had been killed.
Afghan officials told BBC that 12 children and two women were killed in the air strike.
The generals' statement added that investigation had already been launched and that the International Security Assistance Force (ISAF) would ensure that we make compensation to the families according to Afghan culture.
Karzai's office said that the president on behalf of the Afghan people gives his last warning to the US troops and US officials by calling this incident a great mistake.
A group of people from Sera Cala village brought the bodies of eight dead children, some as young as two years old to Lashkar Gah, capital of Helmand, said a BBC report.