Iran has claimed it will press ahead with its plan to achieve industrial-scale production of nuclear fuel.
Tehran, countering diplomatic reports of delays, reaffirmed its nuclear pledge, made after the UN Security Council imposed limited sanctions on it last month, to start rigging up 3,000 centrifuges at its fuel-enrichment plant.
Experts say that number could enrich enough uranium for power plant fuel, or one bomb within a year.
A senior diplomat familiar with International Atomic Energy Agency inspections in Iran said today there is no evidence yet that Tehran had started centrifuge installation in the cavernous underground section of the Natanz enrichment complex, but said there were indications this could begin in a few days.
"We are moving towards production of nuclear fuel which needs 3,000 centrifuges and more than that," a Iranian government spokesman told a weekly news conference.
Iran has vowed not to shelve enrichment work. It says its nuclear programme is solely aimed at generating electricity.
But the United States and the European Union suspect Tehran is seeking to build nuclear bombs and say it will face broader, financially harsher sanctions if it ignores the UN resolution, which gave Iran 60 days to stop enrichment activity.
Iran already operates two experimental cascades of 164 centrifuges, which spin at supersonic speeds to purify uranium.