WASHINGTON - Based in part on secret information provided by the FBI, a federal judge yesterday postponed for six months Dr. Steven J. Hatfill's lawsuit against the government for targeting him in its investigation of the anthrax-laced letters that killed five people in 2001.

U.S. District Judge Reggie B. Walton ordered the government to give him another private update on progress in the case in July, when the FBI says sophisticated tests on the anthrax powder may have revealed more about where it came from. But the judge agreed to put off until at least October requiring the government to answer most of hundreds of questions submitted by Hatfill's lawyers.

Walton said he sympathized with the predicament of Hatfill, a former Army biowarfare expert who has been fired from two jobs since coming under scrutiny in the anthrax case.

"The man's a pariah. Nobody's going to hire him," Walton said.

But the judge said he also understands the government's desire not to let Hatfill's lawsuit interfere with the case. "Obviously we're talking about a very important investigation in which the lives of elected officials were put in jeopardy and the lives of other people were taken," he said, referring to anthrax letters addressed to two U.S. senators.

Walton referred obliquely to secret reports on the progress of the investigation provided to him by the FBI. In light of those reports, which neither Hatfill nor his lawyers have seen, Walton said he would "with reluctance" put off the bulk of the lawsuit until Oct. 7.

The judge said the government should provide to Hatfill's attorneys some limited information it already agreed to give up. He also said Hatfill's attorneys could submit questions to third parties, including news media

organizations that reported leaks from the investigation.

Hatfill, 50, is a U.S.-born physician who trained in southern Africa and became an expert on biological warfare in the 1990s while working as a researcher at the National Institutes of Health and the Army's biodefense center at Fort Detrick.

He was among dozens of biodefense scientists questioned by FBI investigators because of their expertise and possible access to supplies of the Ames strain of anthrax used in the attacks. But while most of the researchers got only fleeting attention, Hatfill became the target of repeated, highly publicized searches, round-the-clock surveillance and intensive news media coverage that apparently relied on leaks.

Hatfill has adamantly denied having anything to do with the anthrax letters. In August, he filed suit against Attorney General John Ashcroft, who had publicly referred to him as a "person of interest" in the case, other top Justice Department and FBI officials, and their agencies.

Walton said he will rule later on whether to dismiss constitutional claims against Ashcroft and other individual defendants, as the government seeks. Legal observers say the major threat to the government is probably not those counts but Hatfill's claim under the Privacy Act against the Justice Department and FBI.

Hatfill, who lives with his girlfriend in Washington, attended yesterday's hearing but did not speak. He slipped out a side entrance to avoid TV cameras staking out the courthouse.