A senior Iranian official has expressed frustration that European states have not delivered on incentives promised last year in return for Tehran's pledge to suspend nuclear enrichment.
"The talks so far do not indicate serious determination of Europeans to achieve any results quickly," Mr Hossein Mousavian, one of Iran's chief nuclear negotiators, told today's Financial Times.
Iran, which denies US accusations that it is seeking nuclear weapons, has agreed to freeze potentially arms-related uranium enrichment activities while the talks continue but has shown impatience with the talks begun late last year.
Germany, France and Britain, acting for the European Union, hope to persuade Tehran to permanently scrap processes such as uranium enrichment - a possible path to the atomic bomb - in return for political and economic incentives.
"We have not yet seen considerable progress in our co-operation and no incentives in political, security, technological, economic and nuclear fields," said Mr Mousavian.
"Now it is time to deliver something to Iranian public opinion and the nation." The EU rejected on Tuesday a call by Iran to speed up talks, insisting the pace of negotiations was right and that the dialogue was on track.
Tehran has so far refused to back down from its position that it be allowed to continue its entire nuclear programme, with guarantees that it will not try to make atomic bombs.
Mr Mousavian said Iran remained committed to the Paris agreement signed last November with France, Germany and Britain, agreeing that a suspension would last until talks conclude.
In his State of the Union address on Wednesday, US President George W. Bush repeated his charge that Iran is developing nuclear weapons and called Iran the "world's primary state sponsor of terror".