Karzai said he got the pledge at a meeting with the agency's station chief, The New York Times reported. The newspaper revealed the payments in a story last week.
The president said described the cash payments as a tiny part of the billions of dollars in U.S. aid given to Afghanistan every year. He called it "nothing unusual" and said the money has mostly gone to rent for officials and medical treatment for wounded members of his guard, although he acknowledged some may have been paid to warlords.
"It has helped us a lot, it has solved lots of our problems," he said. "We appreciate it."