Plans to restart some uranium conversion work, a precursor to uranium enrichment, has sparked diplomatic warnings of UN Security Council involvement.

The fuel production processes had been frozen for the past six months as part of an interim deal with the European Union, but comments attributed to a senior Iranian nuclear official suggest the country could announce a resumption of such activity at any moment.

This follows the adoption of a bill on gaining nuclear technology and requiring the government to maintain the fuel production cycle for producing as much as 20,000 MW from nuclear power. Although the ruling failed to set out a specific date and time for the start of the uranium enrichment process, European countries have expressed their explicit opposition to resumption of the nuclear fuel production cycle.

The comments are believed to refer to work at a uranium conversion facility near Isfahan that is used to convert mined uranium “yellowcake” into uranium tetrafluoride and then into uranium hexafluoride, a feed gas for enrichment centrifuges.

Britain, France and Germany are negotiating on behalf of the European Union and have called a crisis meeting scheduled on 23 May to be held in a European capital and have warned that the move would spark its referral to the UN Security Council, which could impose sanctions. However, Iran feels there is little hope of reaching an agreement, saying the Europeans were hostage to the hardline US position, especially as more than 200 members of the House of Representatives are co-sponsoring a bill that would tighten and codify existing sanctions, and bar subsidiaries of US companies from doing business in Iran.

The Iranian bill was approved by 188 of the 205 deputies but still needs approval from the hard-line Guardian Council to become law. No date has been set for the council’s decision but it was widely expected to be in favour of the measure.