Assistant Attorney General William Bradford Reynolds failed to appear at a Senate hearing on fair-housing legislation for the second time yesterday, and Senate Democrats promised to vote on the bill anyway within the next week.

Sen. Paul Simon (D-Ill.), chairman of the Judiciary subcommittee on the Constitution, had invited Reynolds to testify at the request of two Republican colleagues, Strom Thurmond (S.C.) and Orrin G. Hatch (Utah). But the Justice Department notified the subcommittee shortly before Reynolds' scheduled June 9 appearance and again late Wednesday that he was unable to testify.

The cancellation typifies the kind of guerrilla warfare that often develops between Congress and the administration over sensitive issues. A Democratic subcommittee aide suggested that the Justice Department, which opposes key portions of the bill, may be using delaying tactics.

"We're not waiting for the markup," the aide said. "I don't think further delay would accomplish anything. The subcommittee has no further obligation to Brad Reynolds."

Reynolds' spokesman, Debra Burstion-Wade, said no delay was intended. Reynolds had a scheduling conflict the first time, she said, and his testimony for yesterday's hearing "hasn't cleared the administrative process here by the deadline. There's absolutely no problem as to what the administration's position is."

Justice would not say who held up the testimony, but the Housing and Urban Development Department has differed with Reynolds' fair-housing approach.

Reynolds told the panel in April that the Justice Department opposes the proposal to create a system of administrative law judges who would hear housing-discrimination complaints, order remedies and impose fines. The administration also wants to strengthen the 1968 Fair Housing Act but would rely on lawsuits, which the bill's advocates view as too costly and time-consuming.