A federal judge yesterday ordered that a reporter for the New York Times be jailed for refusing to testify before a grand jury investigating the disclosure of the identity of a CIA operative.

During a hearing in Washington, Judge Thomas Hogan ordered that the journalist, Judith Miller, be incarcerated until she agrees to discuss her reporting with the panel. Under federal law, she could be jailed for up to 18 months. However, the judge stayed his ruling while Ms. Miller pursues an appeal.

The judge said there was ample evidence that prosecutors had exhausted other means of figuring out who leaked the name of Valerie Plame, a longtime CIA employee who sometimes engaged in covert assignments. Some viewed the leak as a politically motivated attempt to intimidate Ms. Plame’s husband, Joseph Wilson, who is an outspoken critic of the Bush Administration.

“The special counsel has made a limited, deferential approach to the press in this matter,” Judge Hogan said. “Ms. Miller has no right to refuse to answer the questions she now refuses to answer.”

In a statement issued after the hearing, the publisher of the Times, Arthur Sulzberger Jr., blasted the prosecution’s tactics.

“The government’s investigation into the Valerie Plame case has moved dangerously off course,” Mr. Sulzberger said. “Judy Miller has done nothing wrong. She is not the person who revealed the identity of a CIA agent. Yet she is the one who is facing time in jail while the very people who exposed Ms. Plame remain unpunished.”

Ms. Miller said she was “extremely disappointed” with the decision. She also noted that she never wrote a story about Ms. Plame.

“It’s frankly frightening that just for doing my job and talking to government employees about public issues, I may be deprived of my freedom and family,” Ms. Miller said. “Confidential sources, especially in Washington, are vital for balanced reporting if the public is to hear from government critics.”

The conversations presently at issue in Ms. Miller’s case do not appear to involve government critics. Rather, the special prosecutor in the case, Patrick Fitzgerald, has asked Ms. Miller to testify about her contacts with the vice president’s chief of staff, Lewis Libby.

Mr. Libby has signed a waiver releasing the journalists he spoke with from any pledge of confidentiality.

Several other reporters have testified about their conversations with Mr. Libby, but Ms. Miller has declined. A lawyer for the Times said it was impossible for the newspaper to know if Mr. Libby’s waiver had been coerced.

One of the reporters who did testify about his discussion with Mr. Libby, Matthew Cooper of Time Magazine, has now been called to testify on a broader range of subjects.

An attorney for Mr. Cooper and Ms. Miller, Floyd Abrams, said Judge Hogan set a hearing next week at which Mr. Cooper may be ordered to jail.

“The judge today ordered Mr. Cooper to answer additional questions. If he does not, and I expect he will not, I expect he will be held in contempt,” Mr. Abrams said in an interview.

A spokesman for Mr. Fitzgerald, the Chicago-based prosecutor, declined to comment on the judge’s rulings.

An advocate for the rights of journalists, Gregg Leslie of the Reporters Committee for Freedom of the Press, said the dispute is likely to end up at the Supreme Court.

“It’s become the new standard-bearer for what the Justice Department is doing wrong in dealing with reporters,” Mr. Leslie said. “It’s not just the typical case. It’s the ultimate one.”

Ms. Miller and the Times are also fighting a legal battle with Mr. Fitzgerald on another front. Last week, the newspaper filed suit in federal court in New York in an effort to block subpoenas the government said it planned to send out for the telephone records of Ms. Miller and another reporter.

Those subpoenas are part of a government probe of whether the Times tipped off an Islamic nonprofit organization, the Global Relief Foundation, about an imminent raid by federal investigators. Prosecutors say the tip-off may have caused evidence to be destroyed and could have endangered law enforcement personnel.

Mr. Abrams has denied that the newspaper alerted Global Relief to the search.

The Times has hired a former independent counsel, Kenneth Starr, to assist in what is shaping up to be a major legal showdown between the newspaper and federal authorities.