And while one senior Iranian official has indicated that UN inspectors might be allowed to make snap inspections of nuclear facilities, another has raised fears that Iran might be developing nuclear weapons, by announcing that its scientists are working on highly advanced centrifuge designs to enrich uranium.
The IAEA has reported that Iran has failed to comply with the UN deadline for it to stop producing enriched uranium - which can be used to make fuel for reactors and bombs - prompting a demand by the US for tough action by the UN Security Council.
Responding, President Ahmadinejad declared: "The Islamic republic will not negotiate with anyone on its absolute right to use peaceful nuclear technology. This is our red line, and we will never give it up."
Iran halted UN snap inspections of its nuclear facilities in February, after the IAEA decided to report Iran to the Security Council.
Mohammad Saeedi, deputy head of Iran's Atomic Energy Organisation, now says they could be allowed, but only if the issue is returned to the IAEA.
But that's unlikely, and diplomats are now preparing for weeks of wrangling in the Security Council, where the US is pushing for sanctions while Russia and China are opposed to punitive action.