An Iranian nuclear official denied a statement by a Tehran parliamentarian that the country had begun installing 3,000 new atomic centrifuges for uranium enrichment - a process that can make atomic bombs.
The head of public affairs at Iran's Atomic Energy Organisation, was quoted by IRNA news agency as saying no such new devices had been fitted at its Natanz uranium enrichment facility.
The head of parliament's foreign affairs and national security committee, had earlier been quoted as saying Iran had started installing the centrifuges, used to make fuel for power stations or material for atomic bombs.
The UN Security Council imposed sanctions on Iran on December 23rd and gave the Islamic Republic 60 days to suspend uranium enrichment. Diplomats have said inspectors from the UN watchdog, the International Atomic Energy Agency (IAEA), had concluded Iran was ready to start installing the centrifuges. But they said timing the installation was likely to be a political decision.
Moderate politicians in Iran, particularly critics of anti-Western President Mahmoud Ahmadinejad, have been counselling caution and possibly even suspending enrichment, until now a step opposed by Iran.
Ahmadinejad has been blamed by critics for exacerbating the standoff with the West by his fiery speeches, although the final say in nuclear policy and other matters of state lies with Supreme Leader Ayatollah Ali Khamenei, Iran's highest authority.
The United States has said it would be a "miscalculation" if Iran believed it could install the 3,000 centrifuges and still avoid another UN resolution or further pressure. If Iran puts 3,000 machines in place and runs them smoothly, it could make enough material for at least one warhead in a year.
But Iran, the world's fourth largest oil producer, insists its aims are peaceful and it wants to generate electricity. Iran already operates two experimental cascades of 164 centrifuges, which spin at supersonic speeds to purify uranium.
UN sanctions imposed last month banned the transfer of sensitive materials and know-how to Iran's nuclear and missile programmes.
The United States has also imposed sanctions on two big Iranian state banks, ratcheting up the pressure on Tehran.
The Islamic Republic said on Tuesday it was barring entry to 38 IAEA inspectors, who were nationals of Western countries which sponsored the UN sanctions or backed them. The IAEA has urged Iran to review that step.