The American Secretary of State, Hillary Clinton, says the Afghan president Hamid Karzai must set up a major crime tribunal and anti-corruption commission.
Mrs Clinton told ABC television the Afghan government needs to take action against people who have "taken advantage of the money that has poured into Afghanistan" in the past eight years.
She says she has made it clear civilian aid will not be given to government ministries unless the US can track its use.
Mrs Clinton says the goal of the US is to defeat al-Qaeda, and help Afghans defend themselves against the Taliban.
A spokesperson for Mr Karzai says the Afghan leader's administration is "serious" about tackling corruption but Mrs Clinton says he can do better.