If you remember the leadup to the current Iraq war, GW Bush spent well over a year publicly saying "force is a last resort" and "all options are on the table".
Bush: Force last resort on Iran (Saturday, August 13, 2005, CNN.COM)
Bush warns Iran on nuclear plans (August 13, 2005, BBC.CO.UK)
Iran confirms plan to resume uranium conversion (August 7, 2005, International Herald Tribune)
The context is the continuing negotiation with Iran over their nuclear program, which I've covered before. Basically they want to establish their own nuclear power plants, but the issue is the design they've used. The design has intermediate steps which produce weapons grade materials.
Thus, this is an honest nuclear proliferation issue. Is Iran planning to produce nuclear weapons? They claim the nuclear program is for civilian use, but if so then why did they choose a process that produces weapons grade material? It would seem they aren't being fully honest, especially since they weren't telling the world about this program in the first place.
A related question is what right do we outsiders (non-Iranians) have to control whether Iran produces nuclear weapons or not? My understanding is that Iran hasn't fully signed on with the non-proliferation treaties, and that they've certainly been sneaking around the backs of the international nuclear regulators to run their program. The world's governments have agreed (well, at least some of them have done so) that nuclear proliferation would be a bad thing for the world, and that all efforts must be made to quash any further spread of nuclear weapons.
That agreement may, though, have been shoved down the collective throats of the world by the super-powers. It's clear that some countries chafe at the restrictions and want to establish their own presence as nuclear powers. I think Iran is one of these countries.
In any case, we cannot forget that the neocon master plan was to first invade Iraq, and then move on to either Syria or Iran. The goal was establishment of "moderate democracy" in the center of the middle east, which would then make the region more agreeable to U.S. interests. At least that's what they said publicly.
I happen to think that's a smoke screen, because how can you honestly install democracy forcibly upon another country? You can't, so either these neocons are stupid or they're lying. Given their track record I would bet they're lying, and that the real goal is to grab the oil.
Germany attacks US on Iran threat (August 13, 2005, BBC.CO.UK): Germany's leader, Gerhard Schroeder, is returning to his role as vocal opponent to GW Bush's plan. He says "Let's take the military option off the table. We have seen it doesn't work" to which I agree most completely.
I think it would be insane for the U.S. to invade Iran on top of the war(s) we're already fighting in the middle east. Why?