It doesn't matter whether President Barack Obama has a formal meeting with Iranian President Hasan Rowhani, or contrives a more informal conversation or "accidental" encounter on the sidelines of the United Nations General Assembly. The general parameters of a possible deal are already well-sketched out, and the real question is whether they are conditions that the United States would find satisfactory.

Unlike his predecessor, Rowhani seems prepared to be more forthright in addressing the major concern of the international community—including those of his partners China and Russia, whose presidents he met earlier this month at the Shanghai Cooperation Organization summit in Bishkek. He needs to commit Iran to a verifiable system of reassurance that its nuclear program is not committed to development of weaponry. Mahmoud Ahmadinejad's record of bluster and defiance, while it may have played well with some hardline domestic Iranian constituencies, also contributed to Iran's growing international isolation, especially in the economic realms—and his unwillingness to agree to a more transparent process forced even Moscow and Beijing, much against their own economic and strategic preferences, to agree to a more stringent set of economic sanctions which have caused real damage to the Iranian economy.

China would like sanctions eased in order to be able to import more Iranian energy—a desire secretly shared even by some U.S. allies and partners in Asia (including Japan and India). Iran needs the foreign exchange in order to prop up a faltering economy—and Rowhani ran his campaign and won election partly on the strength of his platform to improve relations with the world and so gain some economic relief. In order to move forward, Rowhani has signaled that he is prepared to seriously negotiate to accept real limits on Iran's nuclear program, particularly crossing the last hurdles that would be crucial for weaponization. In return, he would expect a partial suspension of sanctions while the negotiating process is underway—with restrictions being fully lifted once the final accord is reached.

Rowhani's offer to the United States is as follows: Iran will stop any efforts that might be construed as part of a weapons program—and will accept limits and some sort of inspection process. In return, however, Iran keeps the full panoply of domestic capabilities that it is entitled to under the Non-Proliferation Treaty. In regional affairs, Iran might be more prepared to lend its support for stabilization efforts in Iraq and Syria—as it did vis-a-vis Afghanistan in 2001—but is not going to recognize Israel or abandon its support for regional allies (the Syrian government and Hezbollah in Lebanon), even if it might be inclined to use its influence to persuade them to moderate their actions. In response for all of this, Iran would expect firm guarantees from the United States that it would cease and desist any efforts to overthrow the Islamic Republic or provide any support for forces seeking regime change.

Rowhani has apparently made the case to the Supreme Leader Ali Khamanei and other factions within the Islamic Republic that engagement—and a willingness to compromise—may be the best way to keep most of what Tehran has achieved and avoid a military conflict with the United States. He also appears to be counting on assurances he has received that if Iran makes a serious effort to reach out and negotiate, other countries may be prepared to weaken the sanctions regime. His gamble is that Obama's own reluctance to contemplate using force in the Persian Gulf—after all, he has let previous deadlines for diplomacy lapse—will make him more receptive to a deal. Essentially, Rowhani is arguing that in return for altering Iran's external behavior, it expects the United States to butt out of its internal affairs.

Will Obama respond, and more importantly, can he carry the U.S. domestic political process along with him?

Any deal which leaves most of Iran's nuclear infrastructure intact will not be welcomed by significant portions of the U.S. policy community, who worry about Iran's ability to retain "breakout capability" should Iran renege on the deal and wish to quickly move to a weapons program. Moreover, as Ray Takeyh recently noted, the U.S. may not be so willing to give the Islamic Republic a blank check on domestic affairs, pointing out: "Congress could take an important step toward convincing yet another recalcitrant elite that the price of full admission to the international community is not merely restraining its nuclear ambitions but also mending its ways at home."

And to the extent that many in Washington are convinced that sanctions are exerting real pressure on Tehran—and that the regime will become more brittle and vulnerable as they continue—there may be a sense that what Rowhani is offering is "too little, too late."

By how he engages Rowhani this week, the president may signal his willingness to talk. But he is going to find that convincing American skeptics of any deal with Iran may be just as difficult as hammering out the small print of any agreement with Iran.

Nikolas K. Gvosdev, a senior editor at The National Interest, is a professor of national-security studies at the U.S. Naval War College. The views expressed are entirely his own.