Iran has the know-how to produce a nuclear bomb and may already have tested a detonation system small enough to fit into the warhead of a medium-range missile, according to confidential papers.

The “secret annex” to this year’s International Atomic Energy Agency (IAEA) report on Iran summarizes information submitted by intelligence agencies about the country’s work on warheads, detonators and nuclear fuel enrichment.

It is based partly on evidence thought to have been smuggled out of Iran by the wife of a spy recruited by German intelligence.

The papers conclude that Iran already “has sufficient information to be able to design and produce a workable implosion nuclear device,” or atom bomb.

The finding goes beyond America’s public stance and may complicate its efforts at talks in Geneva to prevent Iran acquiring nuclear weapons.

General James Jones, President Obama’s National Security Adviser, said yesterday: “Whether they know how to [build a bomb] or not is a matter of some conjecture. What we are watching is what is their intent — and we have been worried about that intent.”

The secret report, excerpts of which were posted on the internet over the weekend, matches British and French estimates of Iran’s nuclear progress.

Its findings are tentative and not endorsed by the IAEA’s own chief, Mohamed ElBaradei, who emphasized last month that the agency had “no concrete proof” of a military dimension to Iran’s program.

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