Richard Armitage has said he revealed Ms Plame's identity
The case of former CIA officer Valerie Plame and the Niger/Iraq connection has taken a new turn now that the then Deputy Secretary of State Richard Armitage has admitted he disclosed her identity He says that it was "a terrible error".
The revelation about Mr Armitage is the latest development in an affair which has seen federal charges laid against the Lewis "Scooter" Libby, former chief of staff to Vice President Cheney.
Here, the BBC News website world affairs correspondent Paul Reynolds looks at the background to the case.
What is this case about?
Valerie Plame's identity as a CIA officer tracking nuclear proliferation was leaked in an article by columnist Robert Novak shortly after her husband Joseph Wilson, a former US diplomat, published an
article in the New York Times in July 2003. Wilson criticised the Bush administration's use of intelligence before the war in Iraq, undermining its allegation that Iraq had tried to buy uranium from Niger, which Wilson had investigated. President Bush had mentioned Niger in his State of the Union speech.
Deliberately revealing an agent's name is a serious offence in the US and the leak sparked a high-level criminal inquiry.
The inquiry did not result in charges over the revelation of Plame's identity but "Scooter" Libby was charged with perjury and obstructing justice.
In July 2006, Ms Plame and Mr Wilson filed a civil lawsuit against Vice-President Dick Cheney, Mr Libby and presidential adviser Karl Rove, accusing them of being behind the leak and maliciously exposing her identity and destroying her career.
How does the Armitage role change things?
It changes everything because the affair was seen as one in which the administration's leading neo-conservatives took revenge on Joseph Wilson by "outing" his wife. Now it has emerged that her name was given much more informally by an official with no such agenda.
The Washington Post said in an editorial that "one of the most sensational charges levelled against the Bush White House - that it orchestrated the leak of Ms Plame's identity to ruin her career and thus punish Mr Wilson - is untrue."
Robert Novak has said: "I don't believe that it was a conscious leak." He said he had been told about Wilson's wife when he asked an official (now known to be Armitage) why Wilson had been chosen for the Niger inquiry
Why did Armitage keep quiet for so long?"
He says he told Patrick Fitzgerald, the special prosecutor investigating the affair, in 2003 that he might have been the source for the Novak article. He says Fitzgerald told him not to say anything. People are now asking why Fitzgerald pursued others in the case with such determination.
What about Karl Rove, the President's aide?
On 12 July 2006, Novak told Fox News that Rove had replied "Oh you know that, too", when Novak (presumably after speaking to Armitage) put it to him that Plame worked at the CIA. Novak said that their discussion of Plame lasted only about 20 seconds. Rove's lawyers said that Rove's recollection was that he had replied "I've heard that, too."
Mr Rove was under investigation for some months and testified to the grand jury investigating the leak.
Then on 13 June 2006 his lawyer Robert Luskin announced: "On 12 June 12, 2006, special counsel Patrick Fitzgerald formally advised us that he does not anticipate seeking charges against Karl Rove."
The indictment against Mr Libby referred to an "Official A" at the White House with whom Mr Libby discussed the issue. The official told Mr Libby that he had discussed Mr Wilson's wife with columnist Robert Novak who would be writing about her CIA connection. Novak's article on 14 July 2003 was the first time Valerie Plame had been mentioned publicly.
"Official A" was said by the US media to be Karl Rove. Joseph Wilson said at one stage that he would be happy to see Mr Rove marched from the White House in handcuffs.
What are the charges against Mr Libby?
Mr Libby has not been charged with leaking the name. He has been charged with two counts of perjury, two counts of making a false statement and one of obstruction of justice. He could face up to 30 years in prison - up to 10 years on the obstruction charge and up to five years on the others.
However, lawyers say that any sentence would probably be much less because, if he is found guilty, the offences might be taken as part of a single action and run concurrently. He also faces a maximum fine of $1.25m. He has pleaded not guilty.
What is Mr Libby said to have done?
According to a statement from the office of the special prosecuting counsel Patrick Fitzgerald, Mr Libby lied to FBI investigators and the grand jury about how and when he learned that Valerie Plame was a CIA officer and lied about disclosing classified information to reporters.
The information was classified as it is a crime to deliberately and knowingly disclose the name of a secret CIA employee.
He is alleged to have claimed that he learned about Ms Plame's name and job from reporters when he had already been told this by other government officials and Vice-President Cheney. His story, according to Mr Fitzgerald, was that "he was just passing gossip from one reporter to another at the long end of a chain of phone calls." Mr Fitzgerald said: "This is not true, according to the indictment."
Washington Post reporter Bob Woodward since testified that he was told about Ms Plame a month before she was named in a newspaper column. He did not name the official who told him but said it was not Mr Libby.
Woodward also said he had spoken to Mr Libby twice in June 2003 about the Iraq war but Mr Libby had not mentioned Ms Plame. This was at a time when Mr Libby was allegedly active in campaigning against her husband.
It remains to be seen if the admission by Richard Armitage affects the Libby case.
Valerie Plame says she will not drop her lawsuit
What is the background to this case?
In 2001, according to a report from the Senate Intelligence Committee, the CIA was told by an unnamed foreign intelligence service that Iraq had agreed with Niger in West Africa to buy several hundred tons of yellowcake, the refined product from uranium ore.
Subsequently, the foreign service gave the CIA what was said to be the text of the contract for this sale. Since Iraq had no civilian use for uranium, the fear was that it was developing a military programme in defiance of UN sanctions. Vice-President Cheney asked what the CIA thought.
In February 2002, the CIA despatched Ms Plame's husband, former US ambassador Joseph Wilson, to Niger to investigate. He was told to ask whether Niger had been approached, had conducted talks or had made an agreement to sell uranium to "countries of concern," which included Iraq.
Why was Mr Wilson chosen?
The Senate report says that he had been to Niger for the CIA in 1999. His name on that occasion was suggested by his wife, Valerie Plame, who was a covert officer in the CIA's nuclear counter-proliferation division.
The report says that interviews and documents indicated that his wife had suggested his name for this trip as well. She then approached her husband. Mr Wilson was not required to sign a confidentiality agreement.
What did Mr Wilson find?
He found no evidence there had been any sale. Nigerien officials strongly denied there could have been. For a start a French-led consortium controlled its uranium industry. But Mr Wilson found an intriguing possibility that Iraq might have approached Niger.
This suspicion came from a former Nigerien Prime Minister Ibrahim Mayaki. He said he had been urged in 1999 by an unnamed businessman to meet an Iraqi delegation which wanted to "expand commercial relations". As uranium was virtually the only thing Niger had to sell, Mr Mayaki interpreted this to mean that Iraq wanted to discuss yellowcake sales.
However when he actually met the delegation, Mr Mayaki said he steered conversation away from trade, nothing was mentioned on either side and so the issue was not resolved.
Mr Wilson told the Senate Committee staff that he had given the US ambassador in Niger his view that there was "nothing to the story". The ambassador, the Senate report says, had reached the same conclusion.
What impact did Mr Wilson's report have?
The CIA felt Mr Wilson had added no substantial new information, but that his talk with Mr Mayaki had been the most interesting and important aspect. The CIA was inclined to believe that Iraq might have been trying to get yellowcake from Niger.
The State Department continued with the more sceptical view it had expressed earlier. The CIA did not brief the vice-president, despite his earlier interest.
In September 2002, a National Intelligence Estimate included a reference to reports indicating that Iraq had sought uranium from Africa, but this was not included in the key findings as it felt to be subsidiary to the main evidence against Iraq.
Lewis "Scooter" Libby's trial is due to start in 2007
What about the British government claims?
Also in September 2002, the British government published a White Paper stating that "there is intelligence that Iraq has sought the supply of significant quantities of uranium from Africa."
The British government has stuck to its position, with support from the Committee chaired by the former Cabinet secretary Lord Butler, which investigated intelligence and the Iraq war.
The British sources are not known.
Despite its inclination to believe the Niger connection, and possible links to other African sources of uranium such as Somalia, there remained doubts in the CIA about how much weight should be given to the claim.
At one stage the CIA said it had told Congress that "the Brits have exaggerated this issue." Nevertheless it appeared in Mr Bush's State of the Union speech to Congress in January 2003.
Why did President Bush mention the British claim in his State of the Union speech?
US intelligence agencies gave less prominence to the uranium claim than did the British. However, the claim did have some credibility in CIA eyes and the National Security Council wanted it mentioned without revealing the CIA's own information.
So the speech simply said: "The British government has learned that Saddam Hussein recently sought significant quantities of uranium from Africa."
These are the so-called famous 16 words.
Then-Secretary of State Colin Powell did not mention uranium in his speech to the Security Council in February 2003.
Were the documents in the case forgeries?
Yes. In October 2002, Elisabetta Burba, an Italian journalist, was given documents purporting to relate to a sale of uranium by Niger to Iraq. She obtained them from Rocco Martino, a former Sismi (Italian military intelligence) employee who styled himself a "freelance intelligence agent".
He said he got them from an employee at the Nigerien embassy in Rome. Suspicious, Burba passed them onto to the Americans. They appear to have been the same documents which the CIA was told about in 2001.
It was not until early February 2003, shortly before the invasion, that the US government gave these documents to the International Atomic Energy Agency for examination. Soon afterwards a senior CIA Africa analyst said the documents could be fraudulent.
One US analyst had already said they looked "funky."
The IAEA quickly concluded that the documents were forgeries. On 11 March, the CIA itself said it did not "dispute" this conclusion.
On 17 June, the CIA accepted that because the documents were false, it no longer believed there was "enough other reporting to conclude that Iraq sought uranium from aboard."
The source of the forgeries has not been established. Under questioning from an Italian parliamentary committee, Sismi has denied that it had a role in their fabrication or distribution.
When were the "16 words" in the State of the Union speech withdrawn?
In July 2003, the CIA Director George Tenet said the words "should never have been included" in the speech.
"From what we know now, [CIA] officials in the end concurred that the text in the speech was factually correct - ie, that the British government report said that Iraq sought uranium from Africa. This should not have been the test for clearing a presidential address.
"This did not rise to the level of certainty which should be required for presidential speeches, and the CIA should have ensured that it was removed."
When did Joseph Wilson intervene?
Mr Wilson said that the day after the State of the Union speech he told the state department the statement was not borne out by the facts as he understood them. In May 2003, the New York Times reported that an unnamed former ambassador had been to Niger and reported that there had been no uranium sale and documents in the case had been forged.
In June of that year the Washington Post, using Mr Wilson as its source, reported that the former ambassador had had doubts about the uranium sale because dates and names on the contract were wrong. In fact, Mr Wilson had not seen the documents and had "misspoken," as he later put it. But it was a sign that Mr Wilson had decided to go public.
Joseph Wilson: the former ambassador hits back
He then wrote an article under his own name in the New York Times on 6 July called "What I Didn't Find in Africa." He concluded that it was "highly doubtful" that any sale had taken place.
And he went beyond that to attack the Bush administration. "Some of the intelligence related to Iraq's nuclear weapons program was twisted to exaggerate the Iraqi threat," he wrote. He also started to give public interviews.
Why would the White House want to unmask Mr Wilson's wife?
The supposition is that it wanted to undermine Wilson's credibility by suggesting that his wife had put up his name for the Niger trip as a way of enhancing his reputation and perhaps business interests. To do this, Valerie Plame's name and role had to be exposed.
However, since it now appears that Richard Armitage was the original source, the
allegations against the White House have lost a great deal of their power.
According to the indictment against him, Mr Libby was critical of the CIA for "selective leaking" when media stories started appearing about the Niger story and had told Judith Miller of the New York Times on 23 June 2003 that Wilson's wife might work for the CIA. He became even more active after Mr Wilson's New York Times article.
Judith Miller spent nearly three months in prison for contempt of court until she agreed to testify about her conversations with Mr Libby.
Mr Wilson himself also came under criticism. He denied that his wife had played a substantive part in the decision to send him but she did, the Senate report accepts, put up his name. He also claimed in the Washington Post that he had seen documents which he had not and wrongly assumed that Vice-President Cheney had been briefed on his findings. He was also accused of going public in a way that might jeopardise his wife's position.
Mr Wilson remains unapologetic.
Mr Libby's trial is not expected until January 2007. Whether he will plea-bargain - that is plead guilty to some charges in exchange for a lesser sentence - is not known.