By Frances Harrison
BBC News, Tehran
Iran says it will resume uranium enrichment activities within the next few days, in a move which could put talks with Europe in jeopardy.
Iran said the suspension was only temporary
Tehran has said for days that it plans to resume conversion of raw uranium into gas, but it has not said when.
Germany has said such a move could lead to Iran being referred to the United Nations Security Council.
The United States has accused Iran of seeking to build nuclear weapons, a charge Tehran has strongly denied.
The deputy head of Iran's atomic energy organisation, Mohammad Saeedi, told a university conference that the first stage of Iran's suspension of enrichment-related activities would be lifted at its Isfahan site.
Iran is known to be converting uranium yellow cake into gas at the site to make the feed material for centrifuges.
Tehran says it had already converted 37 tons of raw uranium into gas before its suspension came into force.
Earlier, one of Iran's negotiating partners, Germany, warned that a resumption of enrichment would lead to the collapse of talks between Europe and Iran - and might culminate in the referral of Tehran to the UN Security Council.
Iran, however, says it only agreed to suspend enrichment and related activities for a short period, and it is impatient with the pace of progress in negotiations with Europe.
Tehran is also likely to stress that it is not resuming full-blown enrichment, just the preparatory phases.