The Islamic Republic of Iran, which is now nothing more than a government of, by, and for fundamentalist-thugs, is not a regime worthy of talks with the leader of the free world. Neither Iranian "President" Mahmoud Ahmadinejad or "Supreme" Leader Ali Khamenei are in control of their countries. What they are in control of are the fundamentalist Revolutionary Guard Corps, the state-run media, and paramilitary units known best for their use of batons, motorcycles, and their murder of Neda.
The Islamic Republic of Iran no longer speaks for the people of Iran. While President Barack Obama was masterful in applying various forms of pressure upon the establishment in Iran(see; Cairo, promise of diplomacy, middle-ground on nuclear program), it would be a mistake to acknowledge the current regime.
The Iranian establishment still controls the nuclear program, foreign and domestic policy, and the security forces of the country. They still are the ones who can do almost whatever they want without fear from the courts of from the Iranian "media". But the Islamic Republic of Iran is the Sick Man of Asia. Between 60%-70% of the country was born after the Islamic Revolution of 1979, and therefore are not as much victims to reaction as are the few lingering supporters of Mahmoud Ahmadinejad and Ali Khamenei. In ten years, roughly that same percentage of the country would have been born after the Iran-Iraq war. The Islamic Republic of Iran is really an Islamic Reaction of Iran, which is not only outdated by destined for deletion. The average Iranian does not consider the U.S. or U.K. to be their enemy, especially in the age of Obama.
It was said by Ben Smith of Politico back on the 13th of June that the "Obama effect" hit "a wall" in Iran, and that is absolutely correct. The force of this hit has been enough to threaten the wall's collapse. The genie is out of the bottle. The emperor, or Supreme Leader rather, is naked. There is no going back. The Islamic Republic of Iran as we know it is destined to die, and while we may be far from realizing what will take its place, it has become obvious that the current regime can no more be trusted by foreigners to keep its word than it can be trusted by its own people to keep their votes counted and their rights protected.
There is also another major issue facing Iran's establishment; oil prices have remained relatively low, $200-a-day militiamen are not cheap, the economy has been hard-hit by the demonstrations and by the regime's response to those demonstrations, some of the high-ups of the establishment(see; Mojtaba Khamenei) have had tremendous amounts of money frozen, and all of this will keep their horrendous recession going strong beneath the weight of international sanctions.
In short, I agree with Roger Cohen of the New York Times and Trita Parsi of the National Iranian-American Council. Keep pressure on the Iranian regime. Don't acknowledge Ahmadinejad's theft of the election as a victory. Don't waste time with cancer-stricken and not-so-supreme leader Khamenei. Let the Iranians deal with Iran.