“To achieve this goal: Iran should accept more quantitative constraints on the number of its centrifuges,” the report reads. “In return, the P5+1 should countenance the continuation of nuclear research and development in Iran that would enable Tehran to make greater qualitative progress.”

If Iran and the P5+1 “resolve the key issue of enrichment, other pieces of the puzzle stand a better chance of falling into place,” states the new ICG report, provided to Al-Monitor in advance of its release date of Aug. 27.

The issue of the size of Iran’s enrichment capacity has been the key sticking point in negotiations between Iran and the five permanent members of the UN Security Council plus Germany (P5+1) to try to reach a comprehensive nuclear accord, extended last month until late November. Iranian Foreign Minister Mohammad Javad Zarif, European Union foreign policy chief Catherine Ashton and their deputies are due to meet in Brussels Sept. 1 to map out a schedule for negotiations to try to reach the final deal by the extended deadline of Nov. 24 . Diplomats, technical experts and likely foreign ministers from Iran and the P5+1 are expected to meet in New York in September and October, on the sidelines of the UN General Assembly opening session, as they race to meet the deadline for the deal.

The new papers, by former US nuclear negotiator Robert Einhorn, the International Crisis Group (ICG) and the Arms Control Association (ACA), propose a compromise that would have Iran agree to reduce the size of its enrichment program in the near term while allowing it to conduct research on more efficient centrifuges. That would enable Iran to expand its enrichment capacity for energy purposes after the deal expires, if Iran still desires to. The new reports seem to reflect a convergence of expert opinion on possible compromise solutions for a deal.

As negotiators from Iran and six world powers prepare to resume talks next month, two new papers by prominent arms-control experts close to the negotiations offer prescriptions for how to overcome key obstacles to reach a nuclear deal.

Einhorn also urges Iran to accept limitations now in return for freedom later.

“The main concept I was trying to convey is looking at focusing on the factor of time,” Einhorn told Al-Monitor in an interview, referring to his “open letter” to Iran’s nuclear negotiators published Aug. 15 on the Iranian website IRDiplomacy.ir.

“It is hard to reconcile the [Iranian] desire for an industrial-scale [enrichment] capability with [the P5+1] insistence on a small capacity adequate only for research reactors,” Einhorn said. “The best way of trying to reconcile those decisions was to focus on time. And to essentially allow the P5+1 to achieve their goals in the nearer term, and provide an opportunity for the Iranians to achieve their stated goals in the longer term.

“And that is the basic concept of it. During the duration of the comprehensive agreement, Iran would accept a limited [enrichment] capacity. After the expiration [of the deal], it would be entitled to expand to a large-scale capability if it continued to desire to do that,” Einhorn said.

Ali Vaez, senior Iran researcher and the lead author of the new ICG report, told Al-Monitor in an interview Aug. 26 that there are similarities in the approach of the ICG, the ACA and Einhorn.

“I think [Einhorn] and all of us have gradually shifted to one direction, and that is a compromise that basically is based on quantitative concessions on the Iranian side for qualitative concessions on the P5+1 side,” Vaez said.

“At the end of the day, one important principle is, there needs to be further reductions in the number of centrifuges,” Vaez said. “And an important principle on the Iranian side is the need to maintain a program that is meaningful. And that is why we say, if the Iranians compromise on the number of centrifuges, [they can] continue on research and development.” Though “not ideal,” the research and development program “would be fully under [International Atomic Energy Agency] supervision … and have enough reassurances” to avoid a breakout scenario.

Daryl Kimball, executive director of the ACA, said he and Vaez were struck when Einhorn’s open letter was published this month that so many of Einhorn’s ideas were similar to what they were formulating in the ICG/ACA paper, which has been transmitted to all of the P5+1 and Iranian nuclear negotiating delegations.

“I think there is a certain logic that is dictated by the constraints both sides are dealing with, both technical and political constraints,” Kimball told Al-Monitor.

The ICG/ACA proposal, much like the Einhorn paper, “allows for limited centrifuge research, provides fuel-supply guarantees for Bushehr and suggests technical assistance for fuel fabrication that Iran does not have the ability to do for the moment, and allows for Iran to have enrichment capacity in the later phases to meet future potential fuel needs, including and beyond Bushehr,” Kimball said.

“Bottom line, our proposed formula for defining Iran uranium-enrichment capacity may not deliver everything each side wants, but it delivers what each side needs,” Kimball said. “That is reducing Iran’s capacity to produce fissile material for many years to come, and for Iran, this formula not only eases the burden of nuclear-related sanctions, it would still give it a route to pursue a realistic indigenous civilian nuclear-energy program.”

A nuclear agreement is ultimately going to “require painful concessions; there is no doubt about it,” Vaez said. “But any kind of agreement should be measured against the alternative.

“I have a very simple formula in discussing it with negotiators: ‘Something has to give,’” Vaez said. “You can’t have it all.”