Update: Adam Sewer's take, "Don't Panic"
Considering that the instinct in some quarters to panic over the revelation that Iran has a second secret nuclear program, the Obama administration seems to have played this one pretty well. American intelligence appears to have known about the plant for some time, which was part of the reason Iran came forward in the first place. By improving relations with Russia by dismantling the missile shield and making nuclear non-proliferation a focus of the G-20 summit, the president has succeeded in putting the U.S. on high ground diplomatically and embarrassing Iran: first because of the deception, and second because the deception failed. The sanctions that the right has been clamoring for for months can now be applied with more international support.
Update II: Thanks to reader Africana for pointing me towards this Mark Lynch post.
It also demonstrates to the Iranians the quality of Western intelligence and the difficulty of deception and denial -- especially in the atmosphere of (quite warranted) mistrust of their intentions. That may reduce their reasons to oppose the intrusive inspections and monitoring regime which Gary Sick argues is the most likely reasonable negotiated outcome. Such an outcome would be far more in the interests of the U.S., Iran, and Iran's neighbors than any plausible outcome of a military strike, and has to be the target of the engagement process.
So despite what I expect to see swarming the media in the next few days -- wanna bet that John Bolton or John Bolton-equivalent oped is already in production over at the Washington Times Washington Post (sorry, it's hard to tell the difference on foreign policy issues sometimes) -- I actually think that this public revelation makes war less rather than more likely. The timing of the announcement, immediately following the consultations at the UN and the G-20 and just before the Geneva meetings, makes it seem extremely likely that the Obama administration has been waiting for just the right moment to play this card. Now they have. It strengthens the P5+1 bargaining position ahead of October 1, changes Iranian calculations, and lays the foundations for a more serious kind of engagement. So now let's see how it changes the game.