Karzai spoke at a news conference after meeting with Danish Prime Minister Anders Fogh Rasmussen ahead of this week's foreign donors' conference in London.
Karzai acknowledged that Afghanistan suffers from corruption and said steady efforts are needed to resolve the problem.
Karzai said that although Afghanistan was making progress, it would need substantial aid for at least five to 10 years. Karzai is on his first visit to Denmark.
Meanwhile seven Afghans and two Pakistanis were arrested today in the southern Afghanistan city of Kandahar.
(AP)