Robert J. Lujan, 28, the son of Interior Secretary Manuel Lujan Jr., was ordered held without bond yesterday pending a preliminary hearing on a charge that he raped a woman at gunpoint Sunday morning in her northeast Alexandria apartment.

Alexandria General District Judge D.F. O'Flaherty, in an early morning arraignment, revoked the $2,000 bond that had been set by a local magistrate Wednesday night after Lujan's arrest. O'Flaherty scheduled the preliminary hearing for 1:30 p.m. today.

Deputy Commonwealth's Attorney S. Randolph Sengel argued that Lujan should be held without bail, noting the seriousness of the allegations and the fact that Lujan pleaded guilty to cocaine-related charges in 1983 in New Mexico.

Lujan pleaded guilty to one count of possession with intent to distribute cocaine and one count of using a phone to conduct a drug sale, said Robert Stanley Powell, Lujan's attorney. Powell said in an interview yesterday that Lujan served 16 months of a six-year sentence.

Powell asked the court to allow Lujan to remain free on bail, saying that he knew Lujan and his family and that he could not believe Robert Lujan would commit rape.

Powell said in an interview that Lujan had met the woman before, "but Saturday night was the only time he had any more than a casual talk with her. He said their relationship was a consensual one."

Lujan, arrested at his family's apartment in the Marina Towers complex on Slaters Lane, has been accused of entering a 48-year-old woman's apartment about 4:30 a.m. Sunday, threatening her with a shotgun and sexually assaulting her.

Manuel Lujan said shortly after the arrest that his son and the woman had both been out drinking Saturday night. After they met, the woman invited Robert Lujan to her apartment, his father said.

In 1987, Robert Lujan, one of Manuel Lujan's four children, was convicted in federal court in Alexandria of driving while intoxicated and driving with a suspended license. Lujan served six months in prison on those charges and was ordered to serve another six months of his 1983 sentence.

Steven Goldstein, a spokesman for Manuel Lujan at the Department of the Interior, said that the secretary did not accompany his son to yesterday's hearing because he did not want anyone to assume he would use his position to help his son.

"He understands that showing up there could be misperceived, and he didn't want that to occur. He didn't want to give any sense of impropriety," Goldstein said.

"Clearly the secretary and Mrs. Lujan feel the anguish that any parent would feel under the circumstances. But Secretary Lujan will not interfere with the system of due process," Goldstein said.