What Happens If Obama's Iran Initiative Fails?

I think Gary Rosenblatt's New York Jewish Week editorial gets the Iran conundrum exactly right:

For now, we must do all we can in support of the administration's efforts to convince Iran to end its nuclear program voluntarily. But Washington needs to address what happens when that fails.

This is the challenge. I support Obama's efforts as well; his strategy is prudent, patient, and well-thought-out. The problem comes if (when?) it doesn't work. I too would very much like to know what President Obama does then.