The Bush administration faces its worst scandal so far with the US Justice Department opening a full criminal investigation into the disclosure of an undercover CIA employee's name.
With the White House rejecting Democrats' demands for the appointment of an independent counsel, the investigation will be conducted by the FBI under the supervision of Attorney General John Ashcroft.
The FBI will now grill Washington journalists and administration officials about claims that President George Bush's chief political and strategic adviser Karl Rowe was among those in the White House who deliberately exposed CIA operative Valerie Plame.
US law carries a maximum of 10 years in prison and $ 50,000 in fines for anyone divulging the identity of a covert US intelligence officer.
Ms Plame, an expert on weapons of mass destruction, is the wife of Joe Wilson, a former US ambassador. In July, Wilson charged the White House with misleading the nation over claims of Iraq's attempts to buy uranium from Niger, saying he had been sent to Niger to check such claims in 2002 and found them to be baseless.
Days later, columnist Robert Novak claimed "two senior administration officials" had told him that Wilson had been sent on the Niger mission at his wife's suggestion. Democrats claim a few other journalists, including from Time magazine and NBC News were also tipped off about Ms Plame being a CIA operative by Rove, who referred to "Wilson's wife" being a CIA employee.
In August, Wilson told a public meeting that: "It's of keen interest to me to see whether or not we can get Karl Rove frog marched out of the White House in handcuffs. And trust me, when I use that name, I measure my words."
Speaking on Monday on MSNBC TV, he called the disclosure "pretty despicable. My sources tell me that at a minimum Mr Rove condoned it. I can't say he was responsible or even approved it, but my sources tell me he condoned it."
President Bush welcomed the investigation as "a good thing", declaring that "there's just too many leaks, and if there is a leak out of my administration, I want to know who it is. If the person has violated law, the person will be taken care of."
