KARL ROVE, President Bush’s chief political adviser, is to give 11th-hour testimony to a grand jury investigating the leak of a CIA official’s identity, and faces possible indictment in the case, sources close to the inquiry said last night.

In a highly unusual move that could presage a criminal scandal that reaches to the heart of the Bush Administration, Mr Rove, who has already testified three times, has agreed to appear again, just days before the two-year investigation was due to end.

According to people directly familiar with the inquiry, Mr Rove has been warned by Patrick Fitzgerald, the special prosecutor leading the investi- gation, that he cannot give a guarantee that the White House aide will not be indicted. Mr Fitzgerald, seeking to establish whether any White House officials committed a crime by deliberately leaking the name of Valerie Plame to the press in July 2003, did not give Mr Rove similar warnings before his earlier grand jury appearances.

The politically charged investigation was reignited last week after Judith Miller, of The New York Times, was released after 85 days in jail for her refusal to testify.

She revealed that her source had been Lewis “Scooter” Libby, the chief of staff to Dick Cheney, the US Vice- President.

Matthew Cooper, of Time magazine, and several other journalists have already testified that they spoke to Mr Rove about Ms Plame days before her identity was first revealed in an article by the conservative columnist Robert Novak in July 2003.

The scandal stems from allegations made by Ms Plame’s husband, Joseph Wilson, a former US ambassador. Shortly before Mr Novak’s column, he accused the Bush Administration of twisting prewar intelligence on Iraq.

When his wife’s name appeared in print, Mr Wilson, who says Ms Plame was an undercover CIA agent, accused the White House of deliberately leaking her name to destroy her career and exact revenge on him. Mr Fitzgerald has been investigating that claim since October 2003, in an inquiry that has involved interviews with Mr Bush, Mr Cheney and Colin Powell, the former US Secretary of State.

Mr Cooper told the grand jury in July that he spoke to Mr Rove and Mr Libby before Ms Plame’s name was made public, but he made clear they did not disclose her actual name or suggest that they knew she was a covert agent. It is a crime to knowingly reveal the identity of an undercover agent.

If Mr Rove is indicted, it would be a hammer blow for Mr Bush, bringing the taint of criminal behaviour into the Oval Office at a time when Republicans face mounting sleaze allegations.

No adviser has been closer or more intimately involved in Mr Bush’s political rise than Mr Rove. The White House has already been rocked by last week’s unrelated indictments of Tom DeLay, the Republican House leader. Mr Rove’s lawyer, Robert Luskin, said he had been assured that no decisions on criminal charges have been made. He said Mr Rove would first have to receive a “target letter” that he is about to be indicted. “I can say categorically that Karl has not received a target letter from the special counsel,” Mr Luskin said.

Starting in 2002, Ms Miller’s stories about purported weapons of mass destruction in Iraq bolstered the Bush Administration’s case for going to war and toppling Saddam Hussein. The failure to find the weapons in Iraq provoked heavy criticism of Ms Miller and The New York Times as well as of the Bush Administration. Mr Fitzgerald has characterised Ms Miller’s testimony as key to completing his investigation into the White House role in the disclosure of the CIA agent’s identity.

The grand jury expires on October 28.

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