Ahmadinejad taunts: "Iran's nuclear path is irreversible. The Iranian nation has reached a new point where no power can deter it from moving full speed ahead to reach peaceful nuclear energy."
He's right, because:
1. Sanctions will fail, either (a) because China and/or Russia refuse to sign on, (b) Iran's allies in South America continue to funnel money to them through dummy corporations, thereby circumventing the sanctions, or (c) sanctions will irritate the already distressed Iranian economy and create more resentment towards the international community and more support for Ahmadinejad.
2. Obama ran against Bush's unilateral preemptive strike policy, so it would be political suicide to strike Iran to prevent them from acquiring nuclear weapons. Even if he only chose limited strikes on nuclear research sites (Clinton-style), Iran would strike Israel (and maybe Iraq) in retaliation. Bringing Israel into this would create a full-force war, which would be unpalatable to the administration.
In summary, Ahmadinejad has Obama's number. No viable options exist, because there is no threat of viable action. This is a game of chicken where Obama will swerve at the last second. Unfortunately, we must learn to accept a nuclear Iran.