The top Republican on the Senate Foreign Relations Committee is demanding an explanation for the CIA’s decade-long effort to funnel cash to Afghan leaders, including President Hamid Karzai.

The reported millions in so-called “ghost money” — delivered and accepted in secret as part of a deal between the CIA and Kabul — undermined efforts by Washington to root out rampant corruption and fraud within the Karzai administration, Sen. Bob Corker (R-Tenn.) said Thursday.

“The alleged [CIA] arrangements make accountability impossible and promote corruption at the top levels of the Afghan government, as well as break trust with the American taxpayer,” Corker wrote in a letter to President Obama.