Senior inspectors from the International Atomic Energy Agency (IAEA) will arrive in Iran on Friday to visit nuclear sites, a senior Iranian official said today.
The visit will come in the wake of Iran's declaration last week that it had enriched uranium for use in power stations for the first time, stoking Western suspicions of a covert atomic bomb project.
Iran insists it wants nuclear technology for civilian purposes to satisfy its booming demand for electricity.
IAEA chief Mohamed ElBaradei, who visited Iran last week, said inspectors from the UN nuclear watchdog had taken samples and would report back to the IAEA's board on whether the Iranians had indeed achieved 3.5 per cent enrichment.
The UN Security Council has urged Iran to stop enrichment work and has asked Mr ElBaradei to report on Iranian compliance by April 28th. The IAEA director said Iran had told him it would step up efforts to answer questions on its atomic plans.
Iran has repeatedly vowed to pursue its nuclear activities but said it would co-operate with the IAEA, as a signatory to the nuclear Non-Proliferation Treaty.
The IAEA says it cannot verify Iran's nuclear programme is entirely peaceful despite three years of investigating - but it has found no substantial proof of efforts to build atomic weapons.
In February, Tehran ended snap inspections of its nuclear facilities after it was referred to the Security Council, which can impose sanctions.
The United States will press other major world powers at a meeting in Berlin of the council's five permanent members and Germany on Tuesday to consider targeted sanctions against Iran.
Russia and China oppose punitive measures against Tehran.
Experts say it would take Iran two decades to produce enough highly enriched uranium for one bomb from its current 164 centrifuges. But Iran says it will to install 3,000 centrifuges, which could make enough material for a warhead in one year.
Iranian officials say its Natanz enrichment plant has a capacity for 54,000 centrifuges.