A federal appeals court ruled yesterday that four reporters must answer questions about their confidential sources on stories they produced about former nuclear scientist Wen Ho Lee.

The journalists reported in 1999 that Lee, who had worked at the Los Alamos National Laboratory in New Mexico, was a suspect in the theft of nuclear secrets for China. Lee alleges he was the victim of illegal government leaks to the media and has filed a lawsuit saying his reputation was ruined by disclosures of the investigation.

A three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit found that although journalists have a qualified privilege to protect anonymous sources, it was outweighed by two key factors in Lee's case: The reporters had information central to his lawsuit, and Lee's attorneys had sufficiently exhausted their efforts to find the alleged leakers by interviewing government officials.

Information about the alleged leakers "goes to the heart" of the lawsuit Lee has filed under the Privacy Act, the court said. "If he cannot show the identities of the leakers, Lee's ability to show the other elements of the Privacy Act claim, such as willfulness and intent, will be compromised."

The decision came the day after the Supreme Court rejected appeals from two reporters in another case. Judith Miller of the New York Times and Matt Cooper of Time magazine face going to jail or revealing their sources to a special prosecutor.

The back-to-back decisions against journalists' use of confidential sources have alarmed press advocates and First Amendment specialists.

"A really bad week for reporters," said Lucy Dalglish of the Reporters Committee for Freedom of the Press. "Journalists need to know that when they promise confidentiality now, they may be making the most serious decision in their life."

Aly Colon, who teaches journalism ethics at the Poynter Institute, a journalism think tank in St. Petersburg, Fla., said: "Any reporter who offers confidentiality needs to consider that jail is a real possibility now."

Miller and Cooper face surrendering in coming weeks for a stint in jail that could last 18 months. Many experts believe the only way they could avoid incarceration is to comply with a court order to identify sources to a grand jury investigating whether government officials illegally leaked to the media the identity of a covert CIA operative in 2003. A judge will consider their punishment today.

The reporters in the Lee case are H. Josef Hebert of the Associated Press, James Risen of the New York Times, Robert Drogin of the Los Angeles Times, and Pierre Thomas, formerly of CNN and now at ABC. They face fines of $500 a day. The court ruled that there was insufficient evidence to hold in contempt a fifth journalist, New York Times reporter Jeff Gerth.

The Associated Press said it would seek a review of the decision by the full nine-member appeals court.

Lee was indicted on 59 counts alleging he mishandled nuclear weapons data and eventually pleaded guilty to one count. In his lawsuit, he alleges that leaks about the investigation harmed his reputation.

After the ruling, Lee Levine, lawyer for Hebert and Drogin, said he feels a duty to warn journalist clients that they face a qualitatively different risk when they agree to take information in exchange for keeping sources anonymous.

"It's the latest example in a long string of examples now of courts in this country casting substantial doubt upon something reporters and their lawyers thought was settled long ago -- that reporters have the ability to make and keep promises to their sources," Levine said.

Charles Tobin, who represented Thomas, agreed. He said all reporters may want to consider discussing with sources the possibility that they would be subpoenaed.

H. Josef Hebert is a reporter for the Associated Press.Pierre Thomas, formerly of CNN. is now a reporter for ABC.James Risen is a reporter with the New York Times.