Updated

Karl Rove (search), the White House deputy chief of staff and longtime adviser to President Bush, has agreed to testify again on the leak of a CIA officer's name without protection against indictment, sources close to the investigation said Thursday.

Sources familiar with the turn of events said that Special Prosecutor Patrick Fitzgerald (search) has not yet decided whether criminal charges will be brought against anyone in the case, which centers on whether CIA officer Valerie Plame (search) was illegally outed to the press.

It is a crime to reveal the identity of a covert U.S. agent. Fitzgerald has spent nearly two years interviewing journalists and Bush administration officials in an effort to determine whether the leak of Plame's identity was intentional and politically motivated.

Spokesman Randall Samborn told FOX News Fitzgerald had no comment on the latest development.

While Rove has already appeared before a grand jury at least three times, this is the first time he has been warned his testimony could be used to indict him. U.S. prosecutors must issue a written warning in advance when the possibility of future charges exists.

This latest twist in an often bizarre case that has cast a shadow over the Bush administration comes a week after New York Times reporter Judith Miller (search) agreed to testify and was freed from jail following a three-month stint for refusing to reveal her source in the Plame case.

Miller said she decided to testify only after she received a personal waiver from her source, Vice President Dick Cheney's chief of staff I. Lewis "Scooter" Libby, and obtained a narrow testimony agreement from Fitzgerald.

"My source has now voluntarily and personally released me from my promise of confidentiality regarding our conversations," Miller said in a statement last Thursday explaining her change of heart.

Before being sent to prison, Miller said that she had received a waiver from her source but believed it was coerced by the administration. Miller was sentenced for contempt of court on July 6.

But according to an attorney representing Libby, Miller was assured the original waiver was legitimate.

"We told her lawyers it was not coerced," Joseph Tate told The Washington Post. "We are surprised to learn we had anything to do with her incarceration."

Rove, 55, has been a Bush adviser and confidant since the late 1970s, having previously worked for his father, former President George H.W. Bush. His shrewd — some say ruthless — political acumen has steered the younger Bush's political campaigns for governor of Texas and president of the United States.

But Rove has always insisted he did not know Plame's name and never mentioned it to reporters. Time Magazine reporter Matthew Cooper (search) told the grand jury in July that while Rove never said Plame's name specifically, he identified her as Iraq war critic Amb. Joseph Wilson's wife.

Cooper told the grand jury that he only learned Plame was Wilson's wife after columnist Robert Novak named her in a column the week after Cooper had talked to Rove. Novak has already testified before the grand jury and, unlike Cooper and Miller, was never threatened with jail, prompting speculation he cut a deal with prosecutors.

Shortly after Cooper testified last July, Rove offered to return to the grand jury for additional testimony. Fitzgerald did not accept that offer until Friday, when Miller testified.

Rove's attorney Robert Luskin said Fitzgerald's calling up Rove again has no connection to Miller's testimony and is part of a winding down of the investigation. Luskin told FOX News on Thursday that he was "not aware of any tangent points whatsoever" between Miller's testimony and the fourth request for Rove to appear before the court.

Before Fitzgerald accepted Rove's offer last Friday, he sent correspondence to Rove's legal team making clear that he was offering no guarantee Rove wouldn't be indicted at a later point. Rove was not given any guarantee in previous appearances either, Luskin said.

Luskin said that he was told Fitzgerald currently had no plans to charge anyone in the case and that Rove had not received a target letter, which would be sent to him if he were about to be indicted.

Plame's name was made public in July 2003 when it appeared in Novak's column. Wilson had criticized Bush in a New York Times article for using in his 2003 State of the Union address British intelligence that claimed Iraq had attempted to purchase yellowcake uranium in Niger.

Two months after Novak's article was published, the CIA asked the Justice Department to investigate whether Novak's sources had broken the law by revealing Plame's identity. The investigation is built on the possibility that the leaker or leakers deliberately blew her cover. Opponents of the Iraq war charge that Plame's identity was revealed in retaliation for Wilson's editorial.

Plame has been identified as a nonofficial covert operative for the CIA, which means that she did not pose as an employee of the U.S. government and if detained overseas was not afforded the protections that come with government or diplomatic posts.

Buck Frevell, a former FBI deputy director, told FOX News that it's difficult to say whether a law was broken by revealing Plame's name because many people in the intelligence community probably already knew her since she was not on a covert assignment.

"The grand jury is going to have to try and pin down not only what Karl Rove said but, under the circumstances, whether there was any intention to reveal an identity that was not in fact already public," Frevell said, adding that if prosecutors had "a smoking gun," they probably would go ahead and indict Rove.

"So it may be just trying to pin down certain pieces of information that they have they've garnered since he appeared the last time and to get further information from him. But [testifying] four times is unusual, no question," he said.

Rove's offer to testify again last July could also indicate he has some new information for prosecutors.

"There is very little other justification for him to go before the grand jury now, unless he feels the need to re-explain something to them so they don't do something that puts him in legal jeopardy," said FOX News' senior judicial analysts Judge Andrew Napolitano.

Any charges would have to come before Oct. 28, when the grand jury is dissolved. If Rove is in fact indicted, it could be yet another blow to a president fighting sagging poll numbers.

"If [Rove] is indicted he'll have to resign, he won't need to be told," said Carl Cannon, National Journal's Washington correspondent and co-author of "Boy Genius: Karl Rove, the Brains Behind the Remarkable Political Triumph of George W. Bush."

Rove's campaigns for the president have won him near-legendary status in American politics, and Cannon said if Rove he were indicted, it could hurt Bush as much as his adviser.

"If Rove's indicted, I should think he would have to be convicted to be seriously hurt," Cannon told FOXNews.com. "It would also wound Bush."

FOX News' Carl Cameron and The Associated Press contributed to this report.