All told, tens of millions of dollars have flowed from the C.I.A. to the office of President Hamid Karzai, according to current and former advisers to the Afghan leader.

“We called it ‘ghost money,’ ” said Khalil Roman, who served as Mr. Karzai’s chief of staff from 2002 until 2005. “It came in secret, and it left in secret.”…

Moreover, there is little evidence that the payments bought the influence the C.I.A. sought. Instead, some American officials said, the cash has fueled corruption and empowered warlords, undermining Washington’s exit strategy from Afghanistan.

“The biggest source of corruption in Afghanistan,” one American official said, “was the United States.”

The United States was not alone in delivering cash to the president. Mr. Karzai acknowledged a few years ago that Iran regularly gave bags of cash to one of his top aides.