WASHINGTON (CNN) -- The Justice Department is launching an investigation into who may have leaked the classified identity of a CIA operative, the White House announced Tuesday.
Spokesman Scott McClellen said the White House had been informed Monday night about the probe and that the White House counsel has sent out an e-mail directing staff to preserve all materials that might be related to the leak.
The White House has said it would cooperate in such a probe on the issue but would not launch an internal inquiry.
In July, syndicated journalist and CNN contributor Robert Novak identified the wife of a former U.S. ambassador critical of the Bush administration's handling of Iraqi intelligence. Novak named Valerie Plame as a CIA operative on weapons of mass destruction, citing Bush administration sources.
The ex-diplomat, Joseph Wilson, has said he believes the White House is behind the leak of his wife's identity, an act of retribution for his revelation of flaws in a British prewar intelligence report that said Iraq was trying to buy uranium from Africa. President Bush cited the British report in his State of the Union address.
McClellan said Monday that "there has been absolutely nothing brought to our attention to suggest any White House involvement."
"The president believes leaking classified information is a very serious matter, and it should be pursued to the fullest extent by the appropriate agency, and the appropriate agency is the Department of Justice," McClellan said.
Four Democratic senators, including Minority Leader Tom Daschle of South Dakota, sent letters Monday to Attorney General John Ashcroft and President Bush, making the case for a special counsel to be appointed in the investigation.
"We do not believe that this investigation of senior Bush administration officials, possibly including high-level White House staff, can be conducted by the Justice Department because of the obvious and inherent conflicts of interests involved," said the letters, which also were signed by Sens. Carl Levin of Michigan, Joseph Biden of Delaware and Jay Rockefeller of West Virginia.
Sen. Charles Schumer, D-New York, also angrily denounced the leak Monday.
"What has gone on in this case is one of the most dastardly, despicable things that I have seen in my more than 20 years in Washington and speaks to the lengths of how far some will go to stifle dissent," he said.
The senator also denounced the White House's attitude toward the situation.
"When was the last time that a covert agent's name was leaked, jeopardizing that agent's life, the life of that agent's network, of informants and the security of this country?" Schumer asked. "This is not just another ordinary leak."
Wilson -- a former U.S. diplomat with expertise in African affairs -- visited Niger in early 2002 on behalf of the CIA to investigate the British report about Iraq attempting to buy uranium. Wilson reported finding no evidence to support the allegation. Wilson later wrote about his Niger visit and conclusions in an op-ed piece for The New York Times, published in July.
Wilson told CNN on Monday that the White House "attempted to discredit the messenger who brought the message by dragging my wife into the public square."
Momentum for an investigation is growing, Wilson said, because "one, I think it is a very serious crime, and secondly, this is -- after all -- an administration that promised to restore dignity and honor to the White House, and acting like schoolyard bullies pulling the hair of a little girl, metaphorically speaking, is something that I don't think people appreciate very much."
According to the Intelligence Identities Protection Act of 1982, it is a federal crime to reveal the identity of a covert agent. Anyone convicted of doing so could be sentenced to as many as 10 years in prison and up to a $50,000 fine, depending upon how the source obtained the information.
"This is a serious leak," former CIA Director James Woolsey said. "You can endanger intelligence and people's lives by revealing the identities of CIA case officers, so it's a serious matter."
Secretary of State Colin Powell also called such a leak serious.
"Not only do you put her at risk or any undercover agent at risk by letting it be known that they are an agent, but you also put their sources at risk," Powell told WDIV-TV while attending the U.S.-Arab Economic Forum in Detroit, Michigan.
On CNN's "Crossfire" on Monday, Novak cast doubt on Wilson's allegation that the disclosure was a attempt by the White House to retaliate against him.
Novak said he learned the CIA operative's identity from two senior Bush administration officials in the course of preparing a piece on Wilson's conclusions.
"Nobody in the Bush administration called me to leak this," Novak said.
In addition to Novak, as many as six other journalists may have been told the CIA operative's name, CNN National Security Correspondent David Ensor reported, citing sources. At least one of the journalists spoke to a Bush administration official who revealed the name, Ensor said, but it was unclear who had initiated the call.
Novak said a confidential source at the CIA told him that Plame was "an analyst, not a spy, not a covert operative and not in charge of undercover operatives."
"They asked me not to use her name but never indicated it would endanger her or anybody else," he said.
In his July 14 column, Novak wrote that Plame "is an agency operative on weapons of mass destruction."
CNN's Ensor reported that sources at the CIA said Plame was an agency operative.
"This is a person who did run agents," Ensor said. "This is a person who was out there in the world collecting information."
A senior FBI official said Monday that Justice Department officials had not contacted his agency to begin an investigation into the leak.
"We're waiting for the call, but it hasn't come yet," said Assistant Director Michael Mason, who heads the Washington field office.
Wilson earlier had suggested senior Bush adviser Karl Rove may have been behind the leak of his wife's identity.
However, on Monday he said that mentioning Rove's name "is not to suggest I thought he was the source or ... the authorizer of the source, but really just to kind of say that I think it comes out of the White House political office."
He added that a source told him "Rove is someone who at a minimum would have condoned it and certainly did nothing to knock it down for over a week after the article appeared."
"The outing of my wife was obviously a political or communications move. The head of the political operation is Karl Rove," he said.
Wilson said he has several journalist sources "who have said that the White House was pushing this story after the leak, after the Novak article, and including Karl Rove."
White House spokesman McClellan said he discussed the matter with Rove and that he denied having anything to do with the leak. McClellan said he feels confident the accusation is "simply not true."
McClellan said that if any officials at the White House leaked Plame's identity, they should be fired and pursued to the "fullest extent."
"If anyone in this administration was involved in it, they would no longer be in this administration," he said.
He said that the president urged anyone who had any information on the leak to report it to the Justice Department.