"... and your enemies closer," as the old saying goes.
The Obama administration has indicated that it would enter dialogue with Iran, though it intends to maintain a fairly tough policy. That's a refreshing breath of realpolitik air after eight years of black-and-white absolutism from Washington: diplomacy is, after all, the art of getting one's enemies (not just one's friends) to agree with you. The prior [mal]administration's cartoonish approach to such matters have hardly been of substantial benefit to the US on the global stage, and it's well past time it adopted a more rational stance.
Iran appears to agree that diplomacy - if carried out absent the ideology-driven caricatures and obstinate non-negotiation of the recent past - is worth pursuing, as well.
President Ahmadinejad's recent remarks, while still strident, are far less shrill than the rhetoric we've heard from Tehran for some time. This is good news for a more amicable solution to the frosty relationship the two nations have shared of late. Then again, the situation in Iran is hardly conducive to maintaining a hard line there, either: their current administration's record on domestic issues and foreign relations is far from stellar, and moderate opposition leaders such as Mohammad Khatami are mounting a viable challenge for the top seat and for the legislature in the next election. If Khatami returns to the presidency, Iran will be even more likely to be conciliatory toward the US. Ahmadinejad needs to regain support (from a far more moderate populace than his policies or rhetoric would indicate) if he hopes to keep his post, which may explain his less strident tone.
Dialogue with post-revolutionary Iran has never been a transparent process: the rhetoric on the surface has rarely matched what went on behind the scenes. Too, Iran has more than once reached out in support of the US in adverse situations, the most notable being directly after 9/11. The abrasive clash of ideologes of recent memory, however, has hurt Iran as much as it has hurt US international standing in the region, and this step away from the undiluted opposition coming from Tehran may be as much recognition of that pain as a willingness to cooperate with a rational foreign power.
For its own part, the Obama administration has been fairly clear that the objectives - Iran's abandonment of nuclear development and support for such groups as Hamas and Hezbollah - remain even though the means to achieve those may change. There's plenty of tough talk from Washington these days, but it is talk, not threats or insults. The change in tone is apparently resounding in Tehran.