"It is now up to the Iranian authorities to provide information," said a diplomat close to the UN nuclear watchdog, the International Atomic Energy Agency (IAEA).

Britain, Germany and France called for an emergency meeting in Vienna February 2 of the IAEA board of governors after Iran resumed uranium enrichment work on January 10. Enriched uranium can serve either as fuel for atomic reactors or the raw material for nuclear weapons.

The European trio and the United States want to take Iran before the UN Security Council, which has enforcement powers such as sanctions, in order to put pressure on Tehran to cease all nuclear fuel work and to comply fully with a now three-year-old IAEA investigation into an Iranian atomic program which the United States charges hides secret weapons work.

IAEA director general Mohamed ElBaradei (photo) said in a Newsweek magazine interview earlier this month that if he is not able to confirm the peaceful nature of the Iranian program, "that's a conclusion that's going to reverberate, I think, around the world."

Inspectors want answers

The IAEA deputy director general for safeguards, Ollie Heinonen, was leading a delegation of about six inspectors, the diplomat said.

Another diplomat confirmed the visit would take place.

Heinonen is seeking answers from Iran on five main questions that remain open.

The IAEA wants to be allowed to visit a former military site in Tehran and to get answers to questions about Iran's dealings with an international nuclear black market that supplied it with crucial atomic technology, and about possible nuclear weapons-related work, which may include outfitting missiles to carry nuclear payloads.

Diplomats have told AFP that Iran may have received in 1997 three sophisticated P-2 centrifuges, which are machines capable of enriching uranium, from the black-market network of disgraced Pakistani nuclear scientist Abdul Qadeer Khan.

Iran denies having received imports of such centrifuges.

A diplomat said the IAEA has only recently obtained declassified US intelligence on P-2 centrifuges as well as on alleged work by Iran on adapting missiles for nuclear warheads.

Heinonen is to file a progress report ahead of the February 2 meeting, with a more detailed account coming in March, ElBaradei said Monday.

"Ammunition" for the Security Council?

ElBaradei wants to give Iran until a regularly scheduled IAEA board meeting March 6 to fully comply, when he intends to file a full report, but the United States and EU negotiators Britain, Germany and France are insisting on a written progress report for the February session.

One diplomat said the West is looking for "ammunition" for its case to take Iran to the Security Council.

A European diplomat said: "Cooperation and transparency are already overdue so we hope Iran comes into line with board resolutions" calling for it to cease all nuclear fuel work and to comply with all requests from IAEA inspectors.

The European trio and the United States are trying to convince key Iranian trading partners Russia and China to back their hard line against Tehran.

But diplomats said the two camps still disagreed on the wording of a resolution for the February 2 meeting, with Russia wanting to put off full referral until at least the March IAEA board meeting.