A woman employee of the White House was raped and robbed Wednesday night by a man who walked up to her car at an intersection, claimed to be a policeman, then quickly put a knife to her throat, D.C. police reported.

After placing the knife against the woman's throat through an open window of the car, police said, the man entered the auto, took the wheel, and drove to secluded sections of the city, where he raped the woman twice and threatened to kill her if she looked at him, police said.

The man also demanded all the woman's money before he left the car in Southwest Washington and allowed her to drive home.

Detectives noted last night that before complying with a request by anyone dressed in civilian clothes who contends that he or she is a police officer, a citizen has the right to ask to see identification.

According to the report of the Wednesday night incident, however, the man threatened the woman with his knife almost immediately after accosting her.

Police said the man walked up to the car shortly after 11 p.m. at an intersection in Southeast Washington.

"Don't move this car - I'm a police officer and I want to inspect it," the man was quoted as saying.

Frightened, according to police, the woman froze. Investigators said the man drew a knife, placed it against the woman's throat and ordered her to move from the driver's seat. When she did, he entered the car, and, still holding the weapon, took the wheel.

Police said he drove to an isolated part of the Buzzard Point area where he raped her and told her, "Don't you look at me, or I'll kill you."

Police said he added: "I don't think you're going to live this night out."

After leaving Buzzard Point, police said, the assailant drove over the 11th Street Bridge with the woman, took her to a parking lot and again raped her.

Finally, investigators said, the man demanded all the money the woman was carrying. She turned over $7.50 and the an drove to 8th and K Streets SE, where he left the car.

The woman drove home, telephoned a friend, and at 3 a.m., called police. She was taken to Georgetown University Hospital where she was examined and released. Police said no arrest has been made in the incident.