It seems to me the leaders of Iran have so much to deal with right now that any additional problems thrown their way would effectively delay their nuclear program. They are like a juggler with five or six things in play at once. You don’t have to physically attack the guy to bring his act to an end. Just a momentary distraction is all it takes.
We don’t impose any price whatsoever on them for their mischief. The sanctions are a laugh. They aren’t that big a deal to start with, and anyone who wants to just ignores them with impunity.
Until they start encountering some truly hard choices about just how important their nuclear program is to them, and what they are willing to do without in order to support it, they will simply continue to ‘negotiate’ and go right on with development.
Petreaus' remarks are not offhand, he is clearly the conduit for sending a message from higher up.