Negotiations between Iran and six world powers over implementing a landmark deal to freeze parts of Tehran's nuclear program in exchange for easing sanctions have run into problems over advanced centrifuge research, diplomats said.
The dispute over centrifuges highlighted the huge challenges facing Iran and the United States, France, Germany, Britain, China and Russia in negotiating the precise terms of their November 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 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 -- 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 said.
State Department spokeswoman Jen Psaki said the U.S. was keen to see the interim deal implemented, though she declined to predict the outcome of the latest talks.
She said U.S. Undersecretary of State for Political Affairs Wendy Sherman would be in Geneva on Thursday to discuss the issue with her European Union counterpart, Helga Schmid, and Iran's negotiator, Deputy Foreign Minister Abbas Araqchi.
In December, Al-Monitor, a news website focusing on the Middle East, 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 reported the former U.S. official had suggested this may have played a role in the dispute.
But 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 U.N. 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.
Foreign Minister Avigdor Lieberman meanwhile accused the Iranians of double-speak, saying the Islamic republic signed off on the deal with the West while continuing to pursue nuclear weapons.
"The Iranians have breached the interim agreement signed in Geneva," said Lieberman during a meeting with his British counterpart, U.K. Foreign Secretary William Hague.
"The Iranian announcement about installing new centrifuges with five times the capacity as the previous generation, proves that the Iranians' only intention is to carry on, taking the time they need to reach the goal of procuring a nuclear weapon," he said. He called on Hague to work toward curbing Iran.