This extends a comment I made here.
Rhetoric is how a leadership communicates publicly with its supporters and reaches out to undecideds. The trick is to work out what it is communicating.
In the case of the recent statements by Iran's Supreme Leader, it is pretty clear. The ideology of the regime remains unchanged and the US is still the Great Satan: that is, the Great Tempter, the great source of all the corrupting distractions of the modern world. Given the democratic anti-regime agitation within Iran, this is more true, not less: since full democracy gives sovereignty (which belongs to Allah) to the people. (Hence opponents can be hanged for the "crime" of "enmity against God".) The US notions of separation of church and state, of female equality, religious freedom, open sexuality and the legitimacy of the pursuit of happiness are all affronts to the fundamental principles of the Iranian regime.
For the regime to be conciliatory is to imply that the Great Satan has its positive points. This would undermine its position domestically, not strengthen it.
Whatever chance the Obama Administration's realist (in the international affairs sense) approach of engagement had (very little IMHO), it died as soon as Iranians began to make clear their rejection of the (patently) rigged Iranian Presidential election. It is not clear to me that the Administration has grasped this point. But, of course, this is always the weak point of realist analysis: it tends to take incumbent regimes as givens while not giving due weight to how foreign policy can be driven by the specific logic of a regime's nature rather than always being trumped by the logic of the state's geopolitical position.
In this case, the specific logic of the regime is that it is the instrument of Allah's sovereignty, which is universal. So its foreign policy is to promote acceptance of that sovereignty to reflect and maintain its internal legitimacy as the manifestation of that sovereignty. The Iranian regime has inevitable limitations, including being unable to evade the constraints of Iran's geopolitical position and the resources available to it. Nevertheless, the regime sees itself as a global player: in some ways as the ultimate global player.
There is nothing the US can offer the regime in any permanent strategic sense that it wants (apart from the US's submission to the sovereignty of Allah). The regime's push for nuclear weapons is the culminating military-power expression of its role as the instrument of Allah's sovereignty. What can the West offer Iran which would be worth giving that up? Which would be worth a state whose legitimacy is as the embodiment of Allah's sovereignty accepting indefinitely second rank status?
To ask the question is to answer it. Either the regime collapses or this is all going to end badly.
ADDENDA I have edited this post to make it clearer without changing the argument.
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