For more than a decade, wads of American dollars packed into suitcases, backpacks and, on occasion, plastic shopping bags have been dropped off every month or so at the offices of Afghanistan's president - courtesy of the Central Intelligence Agency. 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 deputy chief of staff from 2002 until 2005. "It came in secret, and it left in secret." The C.I.A. ... has long been known to support some relatives and close aides of Mr. Karzai. But the new accounts of off-the-books cash delivered directly to his office show payments on a vaster scale, and with a far greater impact on everyday governing. 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." Now, Mr. Karzai is seeking control over the Afghan militias raised by the C.I.A. to target ... insurgent commanders, potentially upending a critical part of the Obama administration's plans for fighting militants as conventional military forces pull back this year. But the C.I.A. has continued to pay.