As American and Iranian officials meet June 9 in Geneva, a former spokesman for Iran’s nuclear negotiators, Seyyed Hossein Mousavian, and several physicists at Princeton are proposing a possible solution to the dispute over how many centrifuges Iran can retain under a long-term nuclear agreement.

Their draft proposal, prepared for publication by the magazine Arms Control Today and made available to Al-Monitor, would permit Iran to transition from the rudimentary machines it currently employs to enrich uranium to more-advanced centrifuges over the course of five years. This would reduce the numbers of centrifuges Iran would require to meet the needs of even an expanded civilian reactor program, but it still raises concerns about Iran’s ability to “break out” and produce fuel for nuclear weapons.

To deal with these concerns, the authors — Mousavian, Alexander Glaser, Zia Mian and Frank von Hippel — suggest that Iran and the five permanent members of the UN Security Council plus Germany, the P5+1 nations, explore creating a multilateral uranium enrichment facility that could supply Iran and other countries in the region with nuclear fuel. Such an arrangement, they say, “could provide a long-term solution to the proliferation concerns raised by national enrichment plants in the Middle East and elsewhere.”

The number and type of centrifuges Iran operates is a major sticking point in the negotiations that have been held in Vienna, New York and Geneva. Senior Iranian and American officials are meeting this week to try to work out understandings before the next P5+1 meeting, scheduled for June 16 in Vienna. Iran, which currently possesses about 18,000 IR-1 machines, of which about 10,000 are operating, has suggested that it needs as many as 100,000 to produce fuel for its sole, operating civilian nuclear power plant at Bushehr when a current contract with Russia to supply fuel for the plant expires in 2021. Iran also plans to build as many as five smaller reactors to produce medical isotopes and conduct research.