Negotiations between Iran and six world powers on implementing a landmark November deal to freeze parts of Tehran's nuclear program in exchange for easing some sanctions have run into problems over the issue of centrifuge research, diplomats said.
The dispute over centrifuges highlighted the huge challenges facing Iran and the six powers in negotiating the precise terms of the Nov. 24 interim agreement. If they succeed, they plan to start talks on a long-term deal to resolve a more than decade-long dispute over Tehran's nuclear ambitions.
Among the issues to be resolved in political discussions due to begin in Geneva later this week is that of research and development of a new model of advanced nuclear centrifuge that Iran says it has installed, diplomats said on condition of anonymity.
Centrifuges are machines that purify uranium for use as fuel in atomic power plants, or, if purified to a high level, weapons.
"This issue (centrifuges) was among the main factors in stopping the previous technical discussions on Dec. 19-21," a Western diplomat told Reuters on condition of anonymity.
Other Western diplomats confirmed that centrifuges were a "sticking point" in the talks with Iran but noted that last month's discussions were understandably adjourned ahead of the December holidays.
"As part of the (Nov. 24) agreement, Iran is permitted to engage in R&D (research and development), but that is tempered by the fact that it is prohibited to install new centrifuges, except as required by wear and tear," the first diplomat said.
Western diplomats said they were uncomfortable with the idea of Iran pressing ahead with the development of more advanced centrifuges. But Iran says centrifuge research is crucial.
"We have to make sure our right to research and development is respected," a senior Iranian government official said on condition of anonymity.
Iran and the so-called P5+1 - the United States, France, Britain, Germany, Russia and China - reached a deal on Nov. 24 in Geneva aimed at curbing the Islamic Republic's most sensitive nuclear work, including medium-level 20 percent uranium enrichment, in return for easing some economic sanctions.
Iran is under UN, US and European Union sanctions for refusing to heed UN Security Council demands that it halt all enrichment- and plutonium-related work at its nuclear sites. Tehran rejects Western allegations that it is seeking the capability to produce atomic weapons, saying its nuclear ambitions are limited to the peaceful generation of electricity.