TEHRAN, Iran – Iran said yesterday it has processed several tons of raw “yellowcake” uranium to prepare it for enrichment – a key step in developing atomic weapons – in defiance of the U.N. nuclear watchdog agency.

Converting raw uranium into hexafluoride gas does not violate any agreements Iran has made regarding its nuclear program and was done with the full knowledge of the International Atomic Energy Agency. However, it draws Iran and America – which quickly voiced its disapproval – closer to a showdown before the U.N. Security Council.

The IAEA board of governors specifically demanded last month that Iran stop all enrichment-related activities, and cited the plans to convert raw uranium into hexafluoride gas as particularly alarming. Iran has refused to back down, and its Parliament is studying a bill that would require the government to proceed with the enrichment process over any objections.

Hossein Mousavian, Iran’s chief delegate to the IAEA, would not specify how much hexafluoride gas had been produced, but he said in an interview that a few tons of raw uranium – also known as yellowcake – had been converted.

The conversion process yields nearly the same amount of gas, meaning a few tons would have been produced.

“We have used part of the raw uranium we had. A few tons of yellowcake has been converted,” Mr. Mousavian said.

“We are not in a hurry to do it,” he added. “The amount we’ve produced is [for] an experimental process, not industrial production.”

It also is less than what experts estimate would be required to make a single bomb – something Iran insists it has no intention of doing. A diplomat close to the agency said in Vienna that although the conversion does not contradict Iran’s obligations, it will be viewed by some countries as a provocation.

In America, the White House quickly disapproved, with spokesman Scott McClellan again accusing Iran of pursuing nuclear weapons and saying it must give up the quest.

“The international community is speaking very clearly to Iran: If they continue in the direction they are going we will have to look at what additional action may need to be taken, including looking to the U.N. Security Council,” he said. Last month, the IAEA’s board of governors unanimously passed a resolution demanding for the first time that Iran freeze all work on uranium enrichment, including conversion. The board suggested Iran could ultimately face U.N. sanctions if it defied the demands.

Mr. Mousavian, who also heads the Foreign Policy Committee at Iran’s Supreme National Security Council, said the IAEA “knows of every milligram of uranium converted.”

In Vienna, IAEA spokeswoman Melissa Fleming agreed the process was “being done fully under IAEA’s watch,” but said she could not immediately confirm how far the Iranians had gotten.

Uranium hexafluoride gas is the material that, in the next stage, is fed into centrifuges used to enrich uranium. Uranium enriched to a low level is used to produce nuclear fuel to generate electricity and enriched further can be used to manufacture atomic bombs.

Iran said last month that it had started converting about 40 tons of raw uranium being mined for enrichment, but yesterday’s remarks were the first confirmation Iran had gone beyond creating precursors to the gas. Thus far, Iran has said it is honoring a pledge not to put uranium hexafluoride gas into centrifuges, spin it, and make enriched uranium. That, however, could change soon.

In Iran, the nuclear program is a matter of national pride – an area where the conservative Parliament and reformist government of President Khatami agree. Legislation being drafted by conservative lawmakers to force the government to resume uranium enrichment ultimately is expected to be approved.

Mr. Mousavian said, however, that Iran is ready to guarantee that its nuclear program will not be diverted to military use and to take steps to eliminate concerns.