London and Washington have found themselves in a public disagreement over a British Government claim that Iraq tried to get uranium from the West African state of Niger.
The CIA says it was a mistake to have included it in President George Bush's State of the Union address, but the British Government is standing by it. BBC News Online's Paul Reynolds tries to answer some key questions.
What is the origin of the claim?
A memorandum came to the CIA's notice (from the Italians, according to Time Magazine) which appeared to document the sale or proposed sale of uranium by Niger to Iraq in the late 1990's. Such a sale would have suggested that Iraq was seeking to build a nuclear bomb since it had no civilian nuclear programme.
What did the Americans do?
The CIA sent fomer US diplomat Joseph Wilson to Niger, where he had once been based. He spoke to Niger officials who were in government when the deal allegedly took place. One said that he had been approached in June 1999 by a unnamed businessman about expanding trade between Niger and Iraq. There was an Iraqi delegation in Niger. This raised a suspicion that Iraq wanted to buy uranium ore since Niger has little else to offer.
What did the US envoy conclude?
He concluded, as he wrote in the New York Times on 7 July this year: "It was highly doubtful that any such transaction had taken place." He said that controls on Niger's uranium mining were very strict and under the supervision of the International Atomic Energy Agency (IAEA). He did not mention the memorandum in his report nor did he see it.
What did the CIA do then?
The CIA says that it gave Mr Wilson's report "normal and wide distribution" but that senior Bush administration officials were not told since the Wilson report did not resolve the issue, in the CIA's view. The British Government was not told either.
Why did the British Government mention the claim in its September 2002 dossier on Iraq?
It says that it got its information from a separate source - a "foreign intelligence service" - and that the information was "credible." The foreign service has not been named officially but the Italians have been mentioned in some press reports, though the one report says it could have been the French. But Italy is also named as a source for the CIA so there is a mystery here. If Italy was a common source, where does the British separate intelligence come from?
There is a hint from some sources that it might have to do with the presence in Niger in 1999 of the Iraqi delegation i.e someone on that delegation may have talked, but the British government refuses to say.
Did the CIA challenge the British claim?
Yes, according to a CIA statement which said: "We expressed reservations" but "our colleagues (the British) said they were confident in their reports and left it in their document."
However, the British Foreign Secretary Jack Straw has said that "The CIA believed in the veracity of the claims" because there were other sources of this information as well. The CIA has said that there had been reports that Iraq had tried to get uranium from two other African countries.
The evidence appeared not convince the CIA, though, because it removed a reference to the Niger claim from a presidential speech in October.
Did the CIA and the British share all their information with each other?
No. The British Government admits that it did not give the CIA the details about its information. It claims that it was up to the unnamed foreign intelligence service to do so. Maybe that service gave it to the US as well. The CIA in turn did not tell the British about the Wilson mission. This lack of information sharing is perhaps the most surprising aspect of the affair.
So why did President Bush mention Niger in his State of the Union address?
This was, the CIA Director George Tenet says, "a mistake." Although Mr Bush attributed the report to the British Government, the CIA says that the British information was not strong enough to justify inclusion in such an important speech.
Critics, including Joseph Wilson, say that the White House used the allegation as part of a trend towards overstating the Iraqi threat, though the White House denies this.
Was the original memorandum not found to be a forgery?
Yes. This was the memorandum which came to the CIA and which launched the Wilson mission in 2002. In March this year the head of the IAEA Mohamed ElBaradei told the UN that "these documents are in fact not authentic." The documents were faxes apparently exchanged between Iraq and Niger - but it turned out, for example, that they carried the alleged signatures of people not in the Niger Government at the time. Why they were not found to be forgeries earlier is not known.
Did this not shake British confidence?
Apparently not. Britain is standing by its report from the unnamed foreign intelligence service. Mr Straw has told the Commons Foreign Affairs Committee that the British knew nothing about the memorandum and that the first Britain knew about the forgery was when it was reported in the press.