Is this the right message we should be sending to Iran and the world? Yes, to an extent. I don't think Dubya has ever been a master of wordspeak, and that's harmed him here I think.
Yes, you want to send a message to Iran stating that we view any nuclear program of yours with the deepest suspicion, and if we acquire intel that backs up our suspicions, we will act.
I believe though, that the words "use of force", should not have been used in this case.
That phrase, 1) will bolster the regime's resolve and will encourage them to continue to seek such development and 2) widen the already visable split between the Commander-in-Chief and his top brass.
In other words, the Iranians will most likely see this as a "we dare you" type of comment and will make military commanders question Bush's logic, wondering if the President realizes how stretched the military is with Iraq.
If I'm an Iranian with nefarious intent for nuclear technology, I'm thinkin', "hey, you're gonna be bogged down in Iraq for some time, what are you gonna do in the meantime?"
As far as alternative options are concerned, (and never wanting to leave him out

)
OverlandSailor brought up an interesting point regarding economic sanctions. If we do seek them, and they are placed on Iran, what guarantee do we have that they won't make and end-run, circumvent them, and continue to proceede anyways. If we use Iraq and North Korea as examples of using sanctions and diplomacy as a tool.... things aren't looking good.
Is there a better solution that you can think of to get Iran back to the table of negotiations? In all honesty, no. Why? Because anyone can see that Iran is
determined to persue nuclear technology. That determination, along with the threats that they percieve us and Isreal to be and the idea that they alone will determine their destiny, make any diplomacy very hard.
Do not expect any agreements made between Iran and any part of the international community to not have concessions made in Iran's favor regarding nuclear technology.
So, it becomes a waiting game. Iran is supposedly a decade away from a nuke. So if Iran's pursuit continues, expect the U.S. and other's to keep a microscope on Iran. Because of Iraq, we can't make any take any serious military action against Iran for quite a few years.
So this is the game: For the U.S... Keep an eye on Iran and know what they do when they do it and get the hell out of Iraq as fast as is strategically possible while making steps to re-group for a possible action on Iran.
The game for Iran...proceede with pursuing nuclear power as fast as possible and obtain the ability to make a bomb soon after.