The White House says it believes that Ahmed Wali Karzai is involved in drug trafficking, and American officials have repeatedly warned President Karzai that his brother is a political liability. Numerous reports link Ahmed Wali Karzai to the drug trade, according to current and former officials from the White House, the State Department and the United States Embassy in Afghanistan, who would speak only on the condition of anonymity. Neither the Drug Enforcement Administration, which conducts counternarcotics efforts in Afghanistan, nor the fledgling Afghan anti-drug agency has pursued investigations into the accusations against the president's brother. Several American investigators said senior officials at the D.E.A. and the office of the Director of National Intelligence complained to them that the White House favored a hands-off approach toward Ahmed Wali Karzai. The concerns about Ahmed Wali Karzai have surfaced recently because of the imprisonment of an informant who tipped off American and Afghan investigators to [a] drug-filled truck outside Kabul in 2006. The informant, Hajji Aman Kheri, ... said he had been an informant for the Drug Enforcement Administration and United States intelligence agencies, an assertion confirmed by American counternarcotics and intelligence officials. Ever since the American-led invasion of Afghanistan in 2001, critics have charged that the Bush administration has failed to take aggressive action against the Afghan narcotics trade.