Lawyers in the CIA leaks investigation are concerned that special prosecutor Patrick J. Fitzgerald may seek criminal contempt charges against New York Times reporter Judith Miller, a rare move that could significantly lengthen her time in jail.

Miller, now in her 10th day in the Alexandria jail, already faces as much as four months of incarceration for civil contempt after refusing to answer questions before a grand jury about confidential conversations she had in reporting a story in the summer of 2003. Fitzgerald and Chief U.S. District Judge Thomas F. Hogan have both raised the possibility in open court that Miller could be charged with criminal contempt if she continues to defy Hogan's order to cooperate in the investigation of who may have unlawfully leaked the name of undercover CIA operative Valerie Plame to the media.

The unusual threat in the case underscores the sensitivity of an investigation that has reached the highest levels of the White House and the prosecutor's determination to extract information from reluctant journalists even though he has yet to charge anyone with a crime. What secrets Miller can unlock for Fitzgerald -- and the reasons he has so doggedly pursued her -- have been a subject of considerable mystery.

While media coverage in recent days has focused on conversations White House senior adviser Karl Rove had with reporters, two sources say Miller spoke with Vice President Cheney's chief of staff, I. Lewis "Scooter" Libby, during the key period in July 2003 that is the focus of Fitzgerald's investigation.

The two sources, one who is familiar with Libby's version of events and the other with Miller's, said the previously undisclosed conversation occurred a few days before Plame's name appeared in Robert D. Novak's syndicated column on July 14, 2003. Miller and Libby discussed former ambassador Joseph C. Wilson IV, Plame's husband, who had recently alleged that the Bush administration twisted intelligence in the run-up to the Iraq war, according to the source familiar with Libby's version.

But, according to the source, the subject of Wilson's wife did not come up.

Miller and the Times have said the reporter has chosen jail to keep promises she made to protect the identity of confidential sources. But Libby's attorney, Joseph A. Tate, has told the New York Times that he provided reporters with assurances that they could rely on the waivers releasing them to talk to Fitzgerald. Tate did not return phone calls placed for this story on Thursday and Friday.

Hogan has publicly chided Miller for "alleging" that she was protecting the identity of a source who Hogan said had freed her to speak about their conversations.

Miller has said she was reporting on Wilson's criticism of administration claims that Iraq was seeking uranium for weapons of mass destruction, but did not write a story.

One of Miller's attorneys, veteran First Amendment lawyer Floyd Abrams, yesterday declined to confirm the meeting with Libby or to discuss any waivers his client may have received.

"Judy's view is that any purported waiver she got from anyone was not on the face of it sufficiently broad, clear and uncoerced," Abrams said.

Four other reporters, including two from The Washington Post, have answered some of the prosecutors' questions after receiving specific waivers from their sources, including Libby.

Matthew Cooper, a Time magazine reporter also subpoenaed in the case, avoided Miller's fate July 6 by agreeing to testify about his conversations with Rove. But three days earlier, Cooper's attorney, Richard Sauber, said in an interview yesterday, Fitzgerald told him during negotiations over Cooper's testimony that his client could well face criminal contempt charges.

Fitzgerald was playing "hardball" and "was trying to get Matt and Judy to comply with the judge's order," Sauber said, adding that he did not consider the threat "over the top."

"Fitzgerald indicated personally to me that was one of his options," Sauber said of their July 3 conversation. He quoted Fitzgerald as telling him: "I'm going to ask the judge to remind these people they risk criminal contempt and it is certainly an option for me." Sauber said he is "convinced" that Fitzgerald "still might" file criminal charges against Miller.

Abrams said he remains concerned about the same possibility but hopes it will not come to pass. "Any resort to criminal law would constitute a sad, even tragic, escalation of this controversy," he said.

Sometimes the threat of criminal contempt can be a prosecutor's strongest tool to obtain information. If Fitzgerald seeks a criminal contempt finding, the judge could order Miller held for as much as six more months and impose other penalties. Criminal contempt findings are very rare, legal experts said, because prosecutors usually seek them only in extreme circumstances or when a person engages in a pattern of defying the law.

Fitzgerald spokesman Randall Sanborn yesterday declined to comment on Fitzgerald's intentions.

Sauber said the tactic was not unexpected in light of a recent case involving Rhode Island television reporter Jim Taricani, who was convicted in December of criminal contempt for refusing to reveal the name of the person who gave him an FBI videotape in a corruption investigation.

But in this closely held investigation, federal appeals court judges of very different ideological stripes and Hogan have reviewed secret evidence and have agreed that Miller's and Cooper's claims of a right to protect their sources is outweighed by the public interest in investigating a possible breach of national security.

Legal experts who have monitored the public twists of Fitzgerald's investigation say the prosecutor has been relentless in running down every fact, an approach that may increase the chances he would seek criminal contempt.

"I think Judith Miller is in much graver danger than she might be otherwise, because this prosecutor seems to want to pursue every avenue with a vengeance," said Mary Cheh, a professor of criminal law at George Washington University. "I'd be very worried."

Judith Miller's silence has put her in the Alexandria Detention Center.Miller faces up to four months for refusing to testify.Prosecutor Patrick J. Fitzgerald may raise stakes.Judge Thomas F. Hogan must clear any new contempt order.Cheney aide I. Lewis Libby reportedly spoke to Miller.