In response to Afghan President Hamid Karzai's warning to U.S. and NATO troops over civilian casualty, the White House said the United States takes Karzai's concerns seriously. "We take President Karzai's statement seriously, and we take his concerns about civilian casualty very seriously," said White House Spokesman Jay Carney at a daily briefing session. Carney said the U.S. side will work with the Afghan side to take measures to reduce civilian casualties. He said both the civilian and military leadership of the U.S. side are in regular contact with the Afghan side on the initiatives to reduce civilian casualties in that country. Earlier in the day, Karzai criticized the NATO-led forces over alleged killing of civilians and strongly called for a ban of aerial raids on Afghan houses. "This is my 'last warning' to the NATO forces. No more air strike on the houses of Afghans will be allowed," Karzai told reporters at a news conference in his fortified Palace here in Afghan capital Kabul. The Afghan leader made these comments in the wake of killing of 14 civilians in an air strike Saturday in Taliban hub southern Helmand province.