US officials have confirmed that an Afghan teenager stabbed a 26 - year - old American soldier to death in eastern Afghanistan.The officials said on Monday that the assailant stabbed Sgt. Michael Cable in the neck on Wednesday in the province of Nangarhar. The officials, who requested not to be named as they were not authorized to speak to the media, said the attacker was thought to be about 16 years old. Cable's brother Raymond Johnston said his brother was "prepared before he left for anything that happened" in Afghanistan. Taliban spokesman Zabiullah Mujahid said the boy, identified as Khalid, had taken refuge with the Taliban. He added that Khalid was acting independently when he stabbed the US soldier. The high number of military casualties in Afghanistan has intensified opposition in the United States and other NATO member states to the protracted war in the country. At least 14 US service members have died in March in Afghanistan, occupied by the US-led forces since 2001. According to the United Nations, thousands of Afghan civilians have died and hundreds of thousands more displaced during a more than 11-year long war. The United States and its allies invaded Afghanistan in October 2001 as part of Washington’s so-called war on terror. The offensive removed the Taliban regime from power, but insecurity continues to rise across Afghanistan, despite the presence of about over 100,000 US-led troops.