“When (UN experts) started to look at them, after a few hours of going at it with a critical eye things started to pop out,” the official said, adding a more thorough investigation used up “resources, time and energy we could have devoted elsewhere”.

The US first made the allegation that Iraq had revived its nuclear program last fall when the CIA warned that Baghdad “could make a nuclear weapon within a year” if it acquired uranium. President George W. Bush found the proof credible enough to add it to his State of the Union speech in January.

The International Atomic Energy Agency (IAEA) official said the charge Iraq sought the uranium was to be the “stake in the heart” of Baghdad and “would have been as close to a smoking gun as you could get” because Iraq could only want it for weapons. Once the IAEA got the documents — which took months — French nuclear scientist Jacques Bautes, head of the UN Iraq Nuclear Verification office, quickly saw they were fakes.

Two documents were particularly bad. The first was a letter from the president of Niger which referred to his authority under the 1965 constitution. That constitution has been defunct for nearly four years, the official said. There were other problems with the letter, including an unsuccessful forgery of the president’s signature.

“It doesn’t even look close to the signature of the president. I’m not a (handwriting) expert but when I looked at it my jaw dropped,” the official said.

Another letter about uranium dated October 2000 purportedly came from Niger’s foreign minister and was signed by a Mr. Alle Elhadj Habibou, who has not been foreign minister since 1989.

To make matters worse, the letterhead was out of date and referred to Niger’s “Supreme Military Council” from the pre-1999 era — which would be like calling Russia the Soviet Union. After determining the documents were fakes, the IAEA had a group of international forensics experts — including people from the U.S and Britain — verify their findings. The panel unanimously agreed with the IAEA.

“We don’t know who did it,” the official said, adding that it would be easy to come up with a long list of groups and states which would like to malign the present Iraqi regime. The IAEA asked the US and Britain if they had any other evidence backing the claim that Iraq tried to buy uranium. The answer was no.

IAEA chief Mohamed El-Baradei informed the UN Security Council in early March that the Niger proof was fake and that three months with 218 inspections at 141 sites had produced “no evidence or plausible indication” Iraq had a nuclear program.