US Central Intelligence Agency has secretly handed over tens of millions of dollars to Karzai's office over the last decade, the New York Times said recently in a revelation that provoked anger in both Washington and Kabul.
But Karzai said the bundles of cash -- allegedly packed in suitcases, backpacks and plastic shopping bags -- were used for health care and scholarships, and that full receipts are issued to the Americans.
"It is used for different issues such as treating patients, scholarships for youths... We give receipts for all these expenditures to the US government."
The New York Times alleged that some of funds were used to bribe warlords into supporting Karzai's US-backed government as the international coalition tries to stabilise the country before NATO troops withdraw next year.
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Warlords who fought against both the Soviet occupation in the 1980s and Taliban regime retain huge influence, and many have close links to Karzai's government that came to power after the Taliban were ousted in 2001.
Karzai, who is due to step down next year, declined to confirm how much his office received each month from the CIA and he repeated his earlier thanks to the US spy agency.
Karzai said he had met with US officials and asked them not to halt the cash despite protests in Washington and criticism from Afghan opposition groups.
"This financial assistance should continue, we thank them for it," he said.
When news of the CIA payments broke, Karzai immediately confirmed the reports and has tried to pass them off as a part of the international aid effort to help his country recover from decades of war.
"This is an official deal between two governments," he said. "I say that we should take every drop of money that comes to us so that our budget can be saved.