WASHINGTON (AP) _ Serb forces today began leaving Kosovo, although the pullout started more slowly than was expected while NATO prepared to begin its peacekeeping mission in the province, the Pentagon announced.

``We know that one MUP (special police) unit has left,'' Pentagon spokesman Kenneth Bacon said. ``We'd like to see a lot more flow'' of troops across the border out of Kosovo, the spokesman added. He said the police unit departed the war-torn Serb province at about 7 a.m. EDT, several hours later than NATO had expected.