As top political strategist, Mr Rove is very close to Mr Bush

A trusted Bush political strategist, Mr Rove has denied being behind the leaking of CIA agent Valerie Plame's identity in the media in 2003.

It is alleged Mr Rove spoke to a journalist about the agent, days before her identity was revealed in the press.

Democrats want the White House to reveal all the facts of the case.

"I will not prejudge the investigation based on media reports," Mr Bush said.

"We're in the midst of an ongoing investigation, and I will be more than happy to comment further once the investigation is completed."

This week, Newsweek magazine quoted Mr Rove's lawyer, Robert Luskin, as saying his client did discuss Ms Plame with Time magazine journalist Matthew Cooper in an e-mail, but did not mention her name.

Jailed journalist

Prosecutors are investigating how Ms Plame's identity was revealed in the media in 2003.

PLAME AFFAIR TIMELINE Feb 2002: Joseph Wilson looks into reports that Iraq tried to buy uranium in Niger 6 July 2003: Mr Wilson goes public about investigation 14 July 2003: Columnist Robert Novak writes the trip was inspired by Ms Plame - Matthew Cooper reports that he had similar information 30 September: Justice department launches probe 24 June 2004: President Bush testifies in case 15 July: Cooper and Judith Miller ordered to testify about sources 10 August: Miller and Cooper sentenced for contempt of court 28 June 2005: Supreme Court refuses to hear appeal 6 July: Miller jailed after appeals fail, Cooper agrees to testify Profile: Karl Rove

Deliberate exposure of a covert agent is a criminal offence in the US.

Although Ms Plame's name was leaked in a different newspaper, Mr Cooper and fellow journalist Judith Miller of the New York Times were both ordered to testify about their sources in the case.

Mr Cooper later agreed after Mr Rove apparently said he could do so.

But Ms Miller maintained her refusal - arguing that it was her duty as a journalist to protect her sources - and was jailed.

The affair has led to a tense stand-off between the government and the media over the right of journalists to keep contacts confidential.