Kabul , Afghanistan ( CNN ) -- Apologies are not sufficient when it comes to civilian casualties , Afghan President Hamid Karzai told the NATO commander Sunday , days after a NATO airstrike killed nine Afghan boys . Karzai told Gen. David Petraeus , the commander of U.S. and NATO forces in Afghanistan , that incidents of civilian casualties during coalition military operations are the main reason for tensions in the U.S.-Afghan relationship and he demanded there be no more , according to a statement from Karzai 's office . The comments came in a private conversation between the two men Sunday , according to an official with NATO 's International Security Assistance Force who asked not to be named . Petraeus made a public apology Wednesday for the deaths , which happened the day before in the province of Kunar , along Afghanistan 's eastern border . U.S. President Barack Obama also expressed regret for the deaths , calling it a `` tragic accident . '' A White House statement said Obama and Karzai agreed that such incidents undermine shared U.S. and Afghan efforts in fighting terrorism . The incident happened after insurgents in mountains above a coalition base launched a rocket attack that wounded a U.S. civilian , according to U.S. Lt. Gen. David Rodriguez . Troops returned fire and insurgents later shot another rocket at the troops . Two attack helicopters flew to the location where they were told the rockets originated , identified who they thought were insurgents and killed nine people . Rodriguez said . Later , they found that the slain people were boys cutting wood . Rodriguez called the incident `` a terrible mistake '' and promised disciplinary action if warranted . The statement from Karzai 's office said Petraeus repeated his apology Sunday and promised `` it will not happen again . '' Karzai said the Afghan people are suffering as a result of civilian casualties and that apologizing and condemning these actions can not ease their pain , according to his office . `` The trust of Afghanistan 's government and people definitively depend on this issue , '' Karzai told Petraeus . Recurrence of such incidents , he said , is `` unacceptable . '' The NATO force official said Sunday , `` We take all civilian casualties very seriously . In light of the recent event that tragically killed nine children , commanders have been given the direction to review our tactical directive that is intended to reduce civilian casualties to the absolute minimum . We will continue to reinforce the need to protect the lives of innocent Afghans as we pursue a ruthless enemy . '' Rodriguez said last week such incidents are `` rare '' when considering all the operations the coalition undertakes . He said a lot of time is spent training soldiers on how to engage the right targets and that directives are constantly reviewed . `` We have done much better preventing civilian casualties , '' he said . `` But we acknowledge we have to do better . '' Rodriguez said the military understands families ' grief over such deaths , and he said soldiers `` feel worse than they can express '' when they `` do something terrible like mistakenly killing young boys . '' `` They have to live with that for the rest of their lives , '' he said . Rodriguez also urged Afghans to help their security forces battle insurgents . Karzai previously noted the Tuesday incident occurred less than 10 days after another one `` that left many civilians dead in the same province . '' On February 20 , Kunar Governor Sayed Fazlullah Wahidi said 64 civilians had died in a joint operation by the NATO force and Afghan security forces over several days . The dead included 20 women and 15 children , he said . Petraeus recently directed military commanders in Afghanistan to review changes meant to minimize civilian casualties . He has ordered commanders to brief helicopter attack crews again on the changes , he said . CNN 's Barbara Starr and Matiullah Mati contributed to this report .
CNN have a private talk February 20 on civilian deaths . Petraeus repeats his apology for the death of Two Afghans boys . Obama has already called it a `` tragic accident ''