VIENNA, Sept 21: Iran defied the United Nations on Tuesday by announcing it would go on converting a large amount of raw uranium to prepare it for enrichment, a process that can be used to develop atomic bombs.

The announcement was likely to provoke an angry reaction from Washington and increase suspicion in Israel, which plans to buy 500 "bunker buster" bombs from the United States that could take out Iran's underground atomic facilities.

Gholamreza Aghazadeh, the head of Iran's Atomic Energy Organisation, told reporters that Iran had begun converting 37 tons of raw "yellow cake" uranium to process it for use in nuclear centrifuges - the machines that enrich uranium.

The International Atomic Energy Agency (IAEA), the UN's nuclear watchdog, unanimously adopted a resolution on Saturday calling on Iran to suspend all activities related to uranium enrichment.

"Some of the amount of the 37 tons has been used. The tests have been successful but these tests have to be continued using the rest of the material," said Aghazadeh, one of Iran's vice presidents, who is attending a general conference of the Vienna-based IAEA.

One nuclear expert has said that once converted from yellow cake into uranium hexafluoride, the feed material for enrichment centrifuges, Iran would eventually be able to enrich enough uranium for up to five nuclear weapons.

Iranian President Mohammad Khatami said Iran was determined to press ahead with its atomic programme even if it brought an end to UN checks of the Islamic Republic's nuclear sites.

"We are determined to obtain peaceful atomic technology even if it causes the stop of international supervision," Khatami said. "We have never wanted nuclear weapons. We want peaceful technology."

Iran had told the IAEA this summer that it intended to run what it described as tests of its uranium conversion facility. However, Tuesday's announcement came after the IAEA board of governors passed the resolution on Saturday calling on Iran to halt all activities linked to uranium enrichment.

The resolution said the IAEA board would consider whether "further steps" would be necessary if Iran failed to implement the suspension - which diplomats said would mean a referral to the UN Security Council and possibly economic sanctions. Israel has made it clear it will never permit Iran to become a nuclear power. -Reuters