The offer that Robert Dreyfus thinks the US, thinking it is being generous, may be willing to make to Iran, that allows some enrichment is probably less than the minimum Iran would be willing to agree to. It is also, at the same time, probably more than the United States can commit to giving, as the unresolved nuclear issue is Israel's single greatest piece of leverage against Iran in their regional conflict.
The bottom line, the reason any discussion about the Iranian nuclear issue is probably pointless is that if it is up to Israel, the status quo will continue indefinitely. In that case working against Iran will continue to be the United States' single biggest global diplomatic and strategic priority. And the Obama administration from its very beginning has never given any reason to believe it is not up to Israel.
So any discussion about Iran's nuclear issue has an aspect of "let's pretend" about it. This one is the same. Let's pretend Israel could not veto any accommodation at all that the US and Iran could reach and talk about what elements the US would require and what elements Iran would require, if a deal was possible.
A future US presidential administration may be more independent of Israel than Barack Obama is at which point, taking into account changes in the situation on the ground, discussions like this may actually be useful.
For this post, I plan at least for a while to add terms to all of the categories as I think of them and as commenters suggest them.
What the US would be comfortable offering:1) Airplane parts - the US is willing to end its, objectively illegal and immoral, ban on repairs for Iran's fleet of aircraft
2) Ending nuclear-related sanctions - the US does not want to end most of the US sanctions that were already in place when the nuclear issue arose with the exceptions listed here, but would remove its opposition to Iranian pipelines such as to India and would be willing to remove its most recent sanctions
3) Ending direct sabotage of Iran's nuclear program - the US and its would stop killing Iranian scientists. The US would be free to continue the ban on Iranian acquisition of nuclear-related materials
4) Ending support for separatist movements - the US would be willing to cut off MEK, Kurdish and Balochi separatists, and to end current plans to increase its support for them
5) Non-strategic nuclear power - the US will allow third parties such as Europe or Korea to build nuclear power plants in Iran in any amounts that Iran wants, as long as Iran disclaims control of its fuel cycle. Bushehr would also be put on line under its current fuel arrangement.
6) Guaranteed supplies of nuclear fuel - the United States claims that it will provide guarantees that all of Iran's power plants will be fueled. These guarantees, of course, are entirely meaningless, as the guarantees Iran already has for Bushehr, for the S-300s and in fact, the NPT's guarantee of nuclear technology "without discrimination" is. But the US foreign policy community has adopted a posture of deliberate naivete regarding these supposed guarantees and considers them a valid part of US offers
7) Diplomatic engagement - the US is willing to go as far as put a US embassy into Tehran if Iran was to want that. The US believes it is offering prestige to Iran of the privilege of publicly communicating with the US.
8) Military accommodation - the US is willing to stop constantly claiming that an attack on Iran is on the table. Every time you hear a US official say this, they think they are increasing pressure on Iran to accept US conditions on its nuclear program. It is not working, it is more likely backfiring, but members of the US foreign policy community like to do what they like to do. It makes them feel powerful and virile, but they are willing to stop in the context of a deal.
What the US would want from Iran:1) An Iranian accepted limit to its domestic stock of LEU - The US, in its preferred case, would still formally oppose all Iranian LEU enrichment, but would just end the sanctions it has imposed using the enrichment as a pretext. This is important because the US would try to deny Iran materials and try to ensure, beyond Iran's agreement, that it cannot build an efficient enrichment program. But in the US' preferred case, Iran would agree that its domestic stock of LEU would permanently be less than the one ton level that could possibly be made into a nuclear weapon. Iran's LEU would all be enriched to a maximum of 3.5%.
2) The most restrictive inspection regime ever conceived - The US would want Iran to go far beyond the Additional Protocols and may go as far as to make Iran a precedent for a new more restricted class of NPT signatories that allow inspections for any activity related to any nuclear or weapons related program on their territory
3) An effectively permanent US veto over Iranian nuclear activities - The US would want Iran to not only disclaim the NPT right to withdraw from the treaty but to disclaim any right to unilaterally alter any of the terms of the agreement at any time and under any circumstances. The US is willing to have the terms reviewed periodically, but these reviews must leave the US with the option to deny any change requested by Iran.
I consider the above the basic outline of what the US would, in theory, be willing to offer Iran. In 2011 Israel has a veto and even if Iran was willing to accept this offer the US could not actually make it. This offer would be bad for Iran, but it would take the nuclear issue off of the table and thereby remove an effective way for the US to harm Iranian interests despite the fact that Iran's regional conflict with Israel is not primarily or even importantly nuclear.
This is an offer the US cannot make, but once again, in a posture of willful naivete, US officials and members of the US foreign policy community envision the US making and Iran accepting an offer like the one described above.
What Iran would be comfortable offering:1) A more stringent inspection regime - Iran is willing to implement the Additional Protocols and to go further. Iran is probably not willing to open as much of its military sector as the US would want in the name of nuclear-related inspections, but it is willing to go farther than any country is required to go today
2) A limit to its domestic enrichment - A decent stock of 3.5% LEU, along with ongoing and improving enrichment is likely enough for now. The US preference that the stock be less than one ton is probably not acceptable any more. It probably was a few years ago. There certainly are factions in Iran that now demand more than that. A limit of three tons of only 3.5% enriched LEU is probably acceptable all around, with Iran, for now, willing to export its current 40 or so kgs of 20% LEU and agree not to make more. Once Iran passes 100-150 kgs of 20% LEU, which is about the same milestone as 1 ton of 3.5%, then the Iranian position will harden and it will be much more difficult to get Iran to relinquish that.
3) Non-hostility in Iraq and Afghanistan - I think Iraq is deceptive right now. Iran is waiting to see how it falls into place and not putting any unnecessary stress on that situation. Iran does not want to alarm the US into canceling the withdrawal or sending more cargo-planes full of money to bribe Iraq's legislature. But once the US is out, and the required measures are voted for, Iraq does not have to be a safe place for Americans. If at the point that Iraq is no longer in flux the US and Iran are as hostile as they are today, the US may resume taking very heavy losses of its military, civilian and mercenary personnel there. Afghanistan is similar but Iran does not have as incredible an array of assets there as it has in Iraq. But Iran can make the US' life in Afghanistan, including a dignified and respectable exit, much easier than it would be facing Iranian opposition.
What Iran would want from the US:1) Future unilateral flexibility on its nuclear program - The US' demand that any agreement commit future generations of Iranians to more stringent terms than other countries is not acceptable. Any agreement would have to revert to the regular NPT, or NPT plus AP after some set time period, regardless of any US decision. The period could be as much as ten or even 15 years, but could absolutely not be into the unforeseeable future. The idea that Iran will still be limited, at the US' discretion, to a maximum of one ton of LEU in its domestic stock in 2035 is outrageous and not acceptable.
2) Relaxation of the recent sanctions - I have not seen objective information about what impact the current sanctions are having. So far Iran is able to advance its economy despite them. For example, the India deal has been canceled and now Iranian gas is staying in the ground so that it can be pumped later and maybe sold for a higher price then. Russia canceled the S-300s, but the US isn't attacking anyway. Maybe Iran will just save the money. We don't have objective indications that US recent efforts are unambiguously hurting Iran. On the other hand, harming Iran is certainly the intention. The US stopping would have at least some value one would presume.
3) Ending of nuclear sabotage and US support for Iranian separatism - Iran would expect US support for Kurdish and Balochi as well as the attacks on Iranian scientists to stop
I think today Iran would accept a deal broadly consistent with the above, if one could be offered. As I said earlier, the Barack Obama administration cannot offer the above, or even the much more favorable terms for the US that are outlined in the previous section. If Obama wins reelection, which is the safest bet for now, then this can be revisited in 2016. By that time Iran will certainly require a stock of several tons of 3.5% and several hundred pounds of 20% LEU. By that time, it won't make sense to discuss limits on Iran's stock since they wouldn't be meaningful.
By the time the Barack Obama is out of office, the most likely situation is that the US will have to just adjust to the fact that Iran is essentially fully nuclear capable.