WASHINGTON - Federal prosecutors have accepted an offer from presidential adviser Karl Rove to give 11th hour testimony in the case of a CIA officer's leaked identity but have warned they cannot guarantee he won't be indicted, according to people directly familiar with the investigation.

The persons, who spoke only on condition of anonymity because of grand jury secrecy, said Special Prosecutor Patrick Fitzgerald has not made any decision yet on whether to file criminal charges against the longtime confidant of President Bush or others.

The U.S. attorney's manual requires prosecutors not to bring witnesses before a grand jury if there is a possibility of future criminal charges unless they are notified in advance that their grand jury testimony can be used against them in a later indictment.

Rove has already made at least three grand jury appearances and his return at this late stage in the investigation is unusual.

The prosecutor did not give Rove similar warnings before his earlier grand jury appearances.

Rove offered in July to return to the grand jury for additional testimony and Fitzgerald accepted that offer Friday after taking grand jury testimony from the formerly jailed New York Times reporter Judith Miller.

Before accepting the offer, Fitzgerald sent correspondence to Rove's legal team making clear that there was no guarantee he wouldn't be indicted at a later point as required by the rules.

Rove's attorney, Robert Luskin, said Thursday he would not comment on any ongoing discussion he has had with Fitzgerald's office but that he has been assured no decisions on charges have been made. Rove would first have to receive what is known as a target letter if he is about to be indicted.

"I can say categorically that Karl has not received a target letter from the special counsel. The special counsel has confirmed that he has not made any charging decisions in respect to Karl," Luskin said.

He said that Rove "continues to be cooperative voluntarily" with the special counsel investigation and "beyond that, any communication I have or may have in the future are going to be treated as completely confidential."

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