We have no other choice but diplomacy at this exact moment. Our armed forces are a might stretched already, don't cha think?
Govexec.com ran an article last week that pretty much lays it out- everything we've got, is either already deployed, on it's way to being deployed, or just got back from being deployed, and needs time to recover.
http://www.govexec.com/dailyfed/1009/100109kp1.htm
There once was a time when we had the Armed Forces to fight on two major fronts at once. Then we downsized-- it was on major front, and one "holding action". Then we downsized again and it was two minor conflicts both at once, but not both at full strength (can you say Iraq and Afghanistan simultaniously).
Anybody who thinks we can do anything other than a quick lightning-style airstrike to deal with Iran is kidding themselves, and that wouldn't go over very well in the rest of the world. If we were to do that, just about everybody would be up in arms, including pulling their support in our other missions, leaving us twisting out there.
It simply isn't a pretty picture.
Now, if only we can get China and Russia to help with Iranian pressure, we might be able to make some progress......