Are you totally totally sure? And usually when war breaks out it's way past "flexing muscles time". And maybe you want to elaborate who is pushing the US exactly or better with what, if you mean reactores I have to disapoint you they have every right to have them, I'm sure there are plenty of people who wish we would have never talked to Iran before, but fact is, they have the same right as the US to have a nuklear reactor.
What's pushing the US is a myriad of issues- we need to stabilize the region to ensure our energy supply, Iran is constantly threatening israel, a close ally of ours, and I think we resent their current regime a bit after we put so much effort into them in the 70's with the shah. Saying they are building nukes is a bit lame IMO, if they want nukes all they have to do is buy the fucking things on the black market. They already have rockets, no ICBM's but they do have rockets. I doubt seriously it's in any countries best interest to develop nuclear weapons nowadays, if you nuke a country, you get nuked back and are completely destroyed, so its suicide to use them. Why bother? They know better than to think of nukes as a deterrant, if we invade and they nuke our soldiers, WHOA they are going to be totally destroyed. I think our aggression has more to do with oil, the insurgency in Iraq and them kicking us out after we were close allies for a period of time than them building nukes.