Washington ? Presidential confidant Karl Rove will testify for a fourth time before the federal grand jury investigating the leak of a CIA officer’s identity even though prosecutors have warned they can no longer guarantee he will escape indictment, lawyers said Thursday.

Rove’s offer was accepted by Special Prosecutor Patrick Fitzgerald in the last week as the grand jury’s wraps up its work and decides whether Rove, Vice President Cheney’s chief of staff I. Lewis “Scooter” Libby or any other presidential aides should face criminal charges.

Rove’s lawyer said Thursday that Fitzgerald has assured him that he has made no decisions yet on charges and that his client has not received a so-called target letter, usually the last step before a grand jury indictment.

“I can say categorically that Karl has not received a target letter from the special counsel,” attorney Robert Luskin said.

Luskin said that Rove “continues to be cooperative voluntarily” but that he could not further discuss his dealings with Fitzgerald’s office.

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

Leaking the identity of a covert agent can be a crime, but it must be done knowingly and the legal threshold for proving such a crime is high. Fitzgerald could also seek charges against anyone he thinks lied to investigators or tried to obstruct the case.

For almost two years, Fitzgerald has been investigating whether someone in the Bush administration leaked the identity of Valerie Plame as a CIA officer for political reasons.