President Samuel K. Doe of Liberia, his capital under siege by rebel soldiers, has retained a Washington lobbyist for $800,000 to represent his interests in the United States.

Doe hired Van Kloberg & Associates starting June 1. The firm's owner, Edward van Kloberg, flew to the Liberian capital of Monrovia a week ago to complete the deal, a spokesman said last week. The contract, filed with the Justice Department's office of foreign lobbyists, is for a 19-month period.

"Doe doesn't need public relations right now, obviously," said Mike Hogan, a spokesman for the lobbyist. But Liberia's embassy in Washington has been shut down since the fighting intensified in recent weeks, and Doe needed someone to represent him here, Hogan said.

The effort to topple Doe, a former army sergeant who seized power 10 years ago in a bloody coup, began Dec. 24 when a band of rebels infiltrated from neighboring Ivory Coast. The insurgents are led by a former high-ranking Liberian official, Charles Taylor.

Hogan said his firm's attempts to begin a dialogue with a representative of Taylor in New York have not been successful so far.

Yesterday the Liberian government said it will begin peace talks with the rebels Monday in neighboring Sierra Leone.

Van Kloberg, a former administrative dean at American University, has several African clients, among them Niger, Burkina Faso and Zaire. He has also represented Romania and Iraq.