Khalil Roman, who served as Karzai's deputy chief of staff from 2002 until 2005 told the New York Times: "We called it 'ghost money'. It came in secret, and it left in secret."
The payments are one of Afghanistan's worst kept secrets. However, the details are a clear illustration of the way that dollars lubricate the business of government but may also act against American interests, propping up criminal and patronage networks even as other projects try to dismantle them.
Some of the money may have even ended up with officials linked to the Taleban or the drug trade, according to the newspaper.
"The biggest source of corruption in Afghanistan," one American official was quoted as saying, "was the United States."
Cash payments have been used since the war began in 2001, initially to buy the services of warlords to wage war on the Taleban. Karzai and his aides then asked for the money to be routed through his office, according to a former adviser, so that he could buy their loyalty himself.
The CIA payments began soon after Iranian officials delivered a carload of cash in December 2002 and continued in monthly deposits. The money is used to fund off-the-books expenses, such as paying off parliamentarians, underwriting delicate diplomatic trips or informal negotiations, according to officials. Some still goes to keeping warlords on side, such as Abdul Rashid Dostum, whose militia was backed by the CIA in 2001.
The CIA declined to comment on the report.