Both of these conclusions track with reality, but both are incomplete, because we do not know the tone of these letters, or much about their substance. What we can reasonably assert, however, is that the letter will not have its intended effect. Quite the opposite, according to the Brooking Institution's Suzanne Maloney:
[T]here is simply no plausible scenario in which a letter from the President of the United States to Ali Khamenei generates greater Iranian flexibility on the nuclear program, which the regime has paid an exorbitant price to preserve, or somehow pushes a final agreement across the finish line. Just the opposite—the letter undoubtedly intensified Khamenei's contempt for Washington and reinforced his longstanding determination to extract maximalist concessions from the international community. It is a blow to the delicate end-game state of play in the nuclear talks at the precise moment when American resolve was needed most.
This most recent letter was delivered at an unfortunate moment in the run-up to the putatively climactic negotiations between Iran and world powers scheduled for later this month. The Obama administration has already given the impression that it wants a nuclear deal more than Iran wants a nuclear deal. The U.S. has good reason to want a strong agreement: It could prevent a nuclear-arms race in the world’s most volatile region; it could protect America’s allies, including and especially Israel, Saudi Arabia, and the United Arab Emirates; it could help ensure that Iranian-sponsored terrorists are denied the protection of a nuclear umbrella; and so on. But it is Iran that actually needs a deal more than the U.S. Its economy has nearly been crushed by American-led sanctions, and the ruling regime understands that further domestic economic hardship could pose a threat to its existence.
And yet, it appears, superficially at least, that it is the U.S. that is bending to the demands of Iran. The most recent example comes via official Iranian-state media, which reported that U.S. negotiators have agreed to allow Iran to run 6,000 uranium-enriching centrifuges, which is up from the previous maximum American concession, 4,000, proposed just two weeks ago.
Iranian negotiators could take such premature concessions as signs that more concessions are coming, in exchange for … not very much. Certainly, no broad shift in Iranian strategic thinking seems likely. As Michael Singh, of the Washington Institute for Near East Policy recently observed, “(T)he changes in U.S.-Iran relations have been decidedly one-sided. The central aim of American policy toward Iran in recent years had been to persuade Tehran to make a strategic shift: away from a strategy of projecting power and deterring adversaries through asymmetric means, and toward one that would adhere to international norms and reinforce regional peace and stability. Détente—and, for that matter, a nuclear accord—resulting from such a shift would be welcome by not only the U.S. but also its allies in the region and beyond. Iran does not, however, appear to have undergone any such change.”