Tehran, Iran ? Iran said Wednesday it had 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 the United States — 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 told The Associated Press in an interview that a few tons of raw uranium — also known as yellowcake — had been converted.

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

“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.

In the United States, 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.