The US Central Intelligence Agency (CIA) has at times financed al-Qaeda militants in Afghanistan, according to a new report, Press TV reported.
The $1 million of CIA funds inadvertently ended up in the hands of the al-Qaeda in 2010, the New York Times reported on Saturday.
The CIA had actually allocated the money to a secret Afghan government fund.
But later Kabul was forced to pay al-Qaeda $5 million in ransom to secure the release of one of its diplomats abducted by the terrorist group in neighboring Pakistan.
One fifth of the money was the funds given to the Afghan government by the CIA.
The report said Osama bin Laden, the leader of al-Qaeda, had at first been concerned about the cash, fearing that the CIA might have tainted it with poison, radiation or a tracking device.
He reportedly suggested that the money should be converted to another currency.
The newspaper said al-Qaeda used the cash to buy weapons and provide payments to families of al-Qaeda militants held in Afghanistan.
"God blessed us with a good amount of money this month," Atiyah Abd al-Rahman, the al-Qaeda general manager, wrote to bin Laden in June 2010.
The newspaper said the funds the CIA delivered to the Afghan government of President Hamid Karzai was used to buy the loyalty of warlords, legislators and other important Afghan officials.
It was also used to cover expenses of clandestine diplomatic trips as well as housing for senior government officials.
Afghan officials told the New York Times the cash flow has slowed since Ashraf Ghani became president of the country in September last year.