The attorney for David E. Rivers, a high-level D.C. official who is considered a central figure in a federal investigation of city contracting, said yesterday he had asked a federal judge to impose sanctions against the U.S. attorney for allegedly violating rules of grand jury secrecy.

"We consider virtually everything the government has done, including naming Mr. Rivers as a target, as being a breach of grand jury confidentiality," John F. Mercer, Rivers' attorney, said last night. Although Rivers has not been formally notified that he is a target, Mercer has said that he believes Rivers is a target.

Mercer said the legal action was filed as a grand jury related matter and that he believed the court papers probably were under seal.

He said he was reluctant to discuss the specifics, because "we do not want to stand in the position of doing what the government has done . . . making informal and ambiguous charges."

"We know Mr. Rivers had not done anything wrong," Mercer said.

A spokesman for the office of U.S. Attorney Joseph E. diGenova said last night that it had not received copies of the court filing.

Chief U.S. District Judge Aubrey E. Robinson Jr., who presides over grand jury matters, said he had "never heard" of an instance in which such a legal move has been made in the absence of a formal indictment, pending grand jury subpoena or formal notification that the person is a target of such an investigation.

Robinson's clerk said the judge's office had not been notified that Rivers had filed any legal action, and court offices had closed by the time Mercer announced that the motion for sanctions had been filed.

Rivers went on an indefinite leave of absence from his post as secretary of the District two weeks ago after it was disclosed that the FBI seized two pairs of cowboy boots, powdery residue that tested positive for cocaine and a handgun during a search of Rivers' Southwest town house.