if Iran is the problem. My understanding is:

1. Yes, Iran is almost certainly working towards nuclear weapons.
   
2. It's going to take 5-10 years to build a working weapon, and perhaps 12-15 years to put together an arsenal of weapons that can offer a useful strategic deterrent. (One nuke on its own is hardly useful, except as a suicide gambit of last resort.)

I realise that the concept of non-proliferation is at stake. But military action isn't usually used to deal with proliferation threats.

So where's the problem that supposedly requires military action now?

Meanwhile Korea not only claims to have nukes but is much closer to creating an ICBM system to deliver them, and so realistically has to be considered more of an immediate threat to the entire world.

Also, if there happened to be genuine ex-USSR nukes available on the black market arms dealers' equivalent of eBay, they would offer any rogue state a tempting alternative. So Iran may well have nukes already. In which case it's too late for action.  

This may be too Machiavellian, but I wonder if there's a meta-game being played here by Russia and China, who may want to encourage US military action -  because strategically and politically it's likely to lead to a disastrous weakening of US influence. The US can only consider fighting an extended land war by bringing back the draft, which would be politically suicidal. And the alternative - a nuke first strike - would set the Middle East alight, turn off oil supplies, and leave the Russians holding access to the main reserves.

So I'll suggest again that the problem isn't Iran's nuclear ambitions. The problem is access to oil reserves, and in the bigger picture this is just another variation in the Great Game.