By Richard Allen Greene
BBC News, Washington
Outed CIA operative Valerie Plame and her husband, Bush critic Joseph Wilson, plan to go ahead with a lawsuit against close associates of President George W Bush despite a startling new revelation about the source of the leak that blew Ms Plame's cover, one of her lawyers has said.
The new information "has no impact on the case. This case is about top-level White House officials who conspired against Valerie Wilson," Melanie Sloan, one of the Wilsons' lawyers, told the BBC, referring to Ms Plame by her married name.
Ms Plame and her husband say she was "betrayed"
The Wilsons filed suit in July against Vice-President Dick Cheney; his former chief of staff Lewis "Scooter" Libby; and Karl Rove, George W Bush's top political adviser, accusing them of intentionally revealing Ms Plame's identity to discredit Mr Wilson.
But a new book due out next week claims that the original source of the leak was Colin Powell's former deputy, Richard Armitage.
Mr Armitage - the deputy secretary of state in Mr Bush's first term - was "a member of the administration's small moderate wing", in the words of Michael Isikoff, the co-author of the book, Hubris.
And he let the information slip to columnist Robert Novak more than three years ago not because he was part of an administration plot to exact revenge on Mr Wilson, but because he is "a well-known gossip who loves to dish and receive juicy tidbits about Washington characters", Mr Isikoff wrote in Newsweek magazine, where he works.
Since the Newsweek article first appeared, a number of other news organisations have said they have independently confirmed Mr Armitage's role.
Mr Armitage has made no public comment.
The case has roiled Washington for more than three years, and forced Mr Libby to resign as Mr Cheney's chief of staff when he was charged with obstructing a special prosecutor investigating the case.
No-one has been charged with leaking the information, and experts doubt that the special prosecutor will haul Mr Armitage in front of a jury.
Mr Armitage is not thought likely to face charges
It is a crime intentionally to disclose the identity of an undercover CIA agent, but Mr Armitage reportedly did not know that Ms Plame had been under cover.
Patrick Fitzgerald, the special prosecutor, is understood to have investigated Mr Armitage's actions.
Reports suggest that Mr Armitage himself did not realise he was the source of the leak until months after Mr Novak's 14 July 2003 column disclosing the information.
Ms Sloan, the lawyer representing the Wilsons, seemed to take the "gossip" explanation at face value.
"We can only go on what we have read, which is that Mr Armitage made his statements to Novak in a gossipy fashion and didn't know she was a covert agent.
"If for some reason we find Mr Armitage was more involved, then we can add him as a defendant. It doesn't change the case against Cheney, Libby and Rove."
Mr Libby's trial is expected to begin in January.