The Times said that officials from the International Atomic Energy Agency had complained to US officials last week about the postings of "roughly a dozen" documents from Iraq's pre-1991 nuclear research that contained diagrams, equations and other details for making a nuclear bomb.

The Times cited experts who said the documents "constitute a basic guide to building an atom bomb."

One of the documents, running to 51 pages, covered the technical advances of Iraq's early nuclear program, including 18 pages on the development of its bomb design.

The US government posted the bomb-related documents on a website set up last March to make available to the public a huge archive of Iraqi government papers, hoping that the public would help sift through the archive for useful information government translators did not have time to search for.

The Times said that earlier in the year UN arms control officials had complained about documents on the website that had information on producing extremely dangerous nerve agents sarin and tabun.

The Times added that the website, called the "Operation Iraqi Freedom Document Portal", was shut down Thursday after the newspaper made enquiries about the nuclear-related documents.

Chad Kolton, spokesman for US Director of National Intelligence John Negroponte, told the newspaper in a statement that "while strict criteria had already been established to govern posted documents, the material currently on the website, as well as the procedures used to post new documents, will be carefully reviewed before the site becomes available again."

The Department of Defense set up the "Operation Iraqi Freedom Document Portal" last March under pressure from legislators to find a way to sort quickly through some 48,000 boxes of mostly Arabic documents seized in the 2003 invasion of Iraq.

The idea was to let the public help in reading and translating the documents, with hopes that they might shed light on matters such as deposed Iraqi leader Saddam Hussein's weapons programs.

While many of the documents have proven innocuous, the Times said the nuclear documents were identical to papers presented to the UN Security Council in 2002 in the leadup to the US invasion.

However, the documents the Security Council saw were heavily edited to mask "sensitive information on unconventional arms," the newspaper said.

It added that a senior diplomat in Europe called the documents a "cookbook" for making a bomb.

"If you had this, it would short-circuit a lot of things," the diplomat said.

Peter Zimmerman, a physicist and arms scientist at King's College, London, said the documents were "very sensitive".

However, the United States appeared to have ignored warnings about dangerous documents surfacing on the website.

In June, the Times said, Demetrius Perricos, the acting chief weapons inspector of the Monitoring, Verification and Inspection Commission, complained to the Security Council about the appearance of risky arms information on a public website.

Nevertheless, the nuclear bomb papers were posted on the site in September.

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