The White House, which has been pressuring its allies to punish Iran for its nuclear ambitions, again accused Tehran of trying to build nuclear weapons and urged it Wednesday to suspend all enrichment activities.

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; enriched further, it can be used to manufacture atomic bombs.

Iran said last month that it has started converting about 40 tons of raw uranium being mined for enrichment - plans the international community specifically said it found alarming. Iran maintains its intentions are peaceful energy purposes.

Hossein Mousavian, Iran's chief delegate to the International Atomic Energy Agency, would not specify how much hexafluoride gas had been produced, but said a few tons of raw uranium - also known as yellowcake - had been converted. The conversion process yields nearly the same amount of hexafluoride gas.

''We have used part of the raw uranium we had. A few tons of yellowcake has been converted,'' Mousavian told The Associated Press. ''We are not in a hurry to do it,'' Mousavian said. ''The amount we've produced is [for] an experimental process, not industrial production.''

Iranian and Western nuclear experts agreed that a few tons of yellowcake would produce a few tons of the gas used for enrichment.