When I was asked the question, it was heavily snowing, the air was mild and I ached from night after night of Iran-worry induced insomnia; so I decided to lighten up a bit and came up with this answer, (which I have been happily propagating in several comment sections.)
Iran and the US are this troubled couple that have undergone a violent breakup. They are now pondering whether to get back together or to divorce. The mistress (Israel) is doing all in her might to prevent the reunion. The whore (Saudi Arabia) is doing all in her power to keep Dick, to the eventual detriment of both Iran and Israel!
But a divorce will run the US to (moral/economic) bankruptcy, thus will deprive the mistress and the whore from the moral/material and material/protective support they seek, respectively. So, for now, they let reason talk!
But seriously, I very much share Sophia's and Fleming's thoughts on this. This all could be to appease the public opinion that is heavily against an attack on Iran and wary of Washington's refusal to talk to Iran. (Keep in mind that Iranians have always wanted to talk to US. Evidence? Cooperation with the US against Taliban, Ahmadinejad's letter or the earlier post!) Rice can very well walk out and say "they didn't cooperate!" (And cooperation in the BushCo lingo means "Do as we say!", "You are either with us or against us!") "Thus we are justified to attack!"
Attack? I don't think they will! Iranian resources, markets and culture are better exploitable in peace; as natural nationalism in Iran will not tolerate physical aggression on the soil! And the defeat in Iraq must have certainly taught them something. Even air attacks will not incapacitate Iran. If nothing else, Iran's Geography has always been protective of its national integrity. I will be digging the Iranian press today and will translate if I stumble on interesting bits and pieces. It appears everyone is in a wait-and-see mode!
Footnote: Today, Ahmadinejad is going to Saudi Arabia to visit with King Abdullah. (source, Iranian press and also Herald Tribune; the NYT, Reuters.)
For future reference, here's The New Yorker's frequently cited article by Seymour Hersh, (which ticked me off as "adding wood to the fire.")