Negotiations between Iran and six world powers on implementing the deal reached in November to freeze parts of Tehran's nuclear program in exchange for easing some sanctions have run into problems over advanced centrifuge research, diplomats told Reuters on Wednesday.
The dispute over centrifuges highlighted the huge challenges facing Iran and the six powers in negotiating the precise terms of the November 24 interim agreement.
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.
"This issue (centrifuges) was among the main factors in stopping the previous technical discussions on December 19-21," a Western diplomat told Reuters on condition of anonymity.
Other Western diplomats confirmed that centrifuges remained a "sticking point" in the talks with Iran but noted that last month's discussions were understandably adjourned ahead of the December holidays and not because of the centrifuge issue.
"As part of the (November 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 told Reuters.
In December, Al-Monitor cited a former U.S. official as saying Iran had notified the six powers it wanted to install additional "IR-2m" centrifuges, modified versions of second generation machines. The website also said the former U.S. official suggested this may have played a role in the dispute.
Diplomats now say Iran has told the six countries it wants to press ahead with the development of even more advanced centrifuges than the IR-2m.
Iran is already testing several different new, more efficient centrifuge models at its Natanz research facility, according to the UN nuclear watchdog. Iran's statements last month that it was testing a new advanced centrifuge have not made clear whether it is an entirely new model or a modified version of an installed one.
Western diplomats said they were uncomfortable with the idea of Iran pressing ahead with the development of more advanced centrifuges. Iran says centrifuge research is crucial.
Last week, an Iranian official said that experts from Iran and the P5+1 group of world powers had chosen January 20 to begin implementing the Geneva deal.
The technical talks, which resumed several weeks ago in Geneva, were interrupted when the Iranians walked out over a decision by the United States to blacklist 19 more Iranian companies and individuals, which the Iranians claimed was in violation of the Geneva deal.
Iran only agreed to resume the talks after it was given an "assurance" by EU foreign policy chief Catherine Ashton, who represents the six powers, that the talks would continue in good faith.
The International Atomic Energy Agency (IAEA) believes that Iranian scientists conducted experiments aimed at developing a nuclear arsenal before 2003 and possibly since.
Iran has denied the charges, saying that purported evidence comes from faulty intelligence by the likes of the CIA and Israel's Mossad that Tehran has not been allowed to see.