Mario Loyola thinks the point of no return may have been reached.
The story in essence is that Iran appears to have blocked access by IAEA inspectors to an underground facility where it has been enriching uranium. So far as I know, both the U.S. government and the IAEA are refusing to comment on the story. But if true, this represents a point of no return, which Iran has staged deliberately to catch us off guard while everyone is studying its lengthy answer to the EU3+3 offer. In my piece in the current (August 28) print edition of National Review, I described precisely this eventuality as a point of no return, and argued that the United States should invoke preemption if this ever happened.
Update:
Loyola found out more about the AP story. It was, no surprize to anybody, “accurate but critically imprecise,” meaning that the tipping point has not been reached.