President Bush has announced that his special envoy in Afghanistan, Zalmay Khalilzad, is also to become the new American ambassador in Kabul.
The White House said the appointment of Mr Khalilzad, who was born in Afghanistan, would help to speed up reconstruction efforts there.
Mr Khalilzad replaces the current ambassador, Robert Finn.
His appointment has to be confirmed by the senate.
Last week President Bush asked Congress for an additional $1.2bn for Afghanistan's reconstruction, and $11bn for American military operations there.
From the newsroom of the BBC World Service