The US Justice Department has been asked to look into whether members of the Bush administration broke the law and revealed the identity of an undercover intelligence agent.
No evidence of weapons of mass destruction have yet been found
The Central Intelligence Agency officer alleged to have been publicly exposed is married to a former US diplomat who has accused Washington of exaggerating the threat of the Iraqi weapons programme in the run-up to the war.
The incident is said to have followed public criticism by her husband, Joseph Wilson, of a claim raised by the US president that Iraq had attempted to buy nuclear materials in Africa.
That claim - sourced to British intelligence reports - appeared in Mr Bush's State of the Union speech in January, but the White House later admitted it was a mistake to include it.
According to sources quoted by the Washington Post, the investigation is being carried out at the request of CIA director George Tenet.
The newspaper alleged on Sunday that White House officials called several Washington journalists and revealed the identity and occupation of Mr Wilson's wife - apparently motivated by revenge.
"In matters like this, as a matter of routine, a question like
this is referred to the Justice Department for appropriate action,
and that's what's going to be done," national security adviser
Condoleezza Rice was quoted as telling Fox television on Sunday.
However she said she knew "nothing" of any White House effort to leak such information.
She said the White House would co-operate should the Justice Department decide to proceed with a criminal investigation of the matter.
Joseph Wilson, US ambassador to Gabon 1992-95, revealed in July that he had been sent to look into allegations that Iraq bought processed uranium, that could be used to make nuclear weapons, in the 1990s.
His investigation which took place in February 2002 led him to conclude that it was "highly doubtful" that any such transaction had taken place.
But in an article for a US paper around the same time he asked why, despite the research he submitted to the relevant authorities, the uranium claim had indeed been included in the Bush speech.
Under US law, exposing an undercover intelligence officer is an offence punishable by 10 years in jail.