[Washington Post] The U.S.-led coalition in Afghanistan apologized Friday for mistakenly killing a 2-year-old child during an airstrike, but Afghan President Hamid Karzai said the attack may scuttle a long-term security agreement with the United States.In an angry statement late Thursday, Karzai said a suspected U.S. drone fired into a house shortly before noon in Helmand province, killing the toddler and wounding two women. Karzai said the strike had further shaken his confidence in the behavior of coalition forces, and he vowed that he would not allow thousands of U.S. troops to remain in Afghanistan after 2014 if similar attacks continue.