President Obama has just been presented with what could be the defining moment of his presidency and perhaps a defining moment in world history. On the eve of his speech calling on the nations of the world to seek nuclear disarmament, it was revealed that Iran has a second, secret nuclear enrichment plant.

Iran needs three things to have a nuclear weapon:

1) The fuel. The easiest one to make is enriched uranium. Uranium is a mineral found in the earth that, if enriched a little bit, can be used in nuclear energy plants. Uranium needs to be enriched to a much higher level to make a bomb. Think of it like the spin cycle on your dryer. The more the spin cycle runs the more water is thrown off.

The Iranians claim they’re only spinning for nuclear energy but won’t let us inspect the facilities. So we suspect they’re going all the way.

2) A way to deliver the bomb. If Iran wanted to detonate a nuclear weapon nearby they could just put on the back of a truck. But if they want to attack Israel, or Europe or the United States, they need a long-range missile capable of carrying a nuclear weapon on its tip.
Iran has already tested missiles capable of reaching Israel, Europe and American forces in Iraq. Iran has not yet successfully tested long range missiles, but we know Iranian engineers were on the ground in North Korea when it tested longer range missiles a few months ago.

3) A blueprint. This is the hardest part – if they don’t get it just right the bomb fails to detonate, or detonates at the wrong time. It’s doubtful Iran has scientists and engineers capable of coming up with a blueprint on their own. But the father of Pakistan’s atomic bomb and a notorious nuclear arms merchant, Dr. A.Q. Khan, said recently that he has helped with Iran’s nuclear program. He was under house arrest in Pakistan until a few weeks ago when he was quietly released. No one knows where he is now.

If Iran gets all three of these they will have the bomb. And once they do other nations in the region, like Saudi Arabia, Egypt, and perhaps Turkey, will conclude they need nuclear weapons of their own. A nuclear Iran will set off an arms race-- a nuclear arms race-- in the most dangerous, unstable part of the world. Furthermore, Iran is the state that sponsors terrorist groups like Hezbollah and Hamas and has threatened on a regular basis to wipe Israel off the face of the earth. It has also declared the world would be a better place without America.

If President Obama is unable to stop Iran from getting nuclear weapons, it means he will be unable to stop any country from getting nuclear weapons. Pakistan already has them, North Korea does too. Both countries are unstable and Islamic extremists have set their sights on Pakistan’s nuclear arsenal. Both countries could ignite a nuclear arms race in their regions.

At that point, President Obama’s goal of nuclear disarmament will look like just a pretty speech; the reality would be a world awash in nuclear weapons within a few years. The likelihood of one be used, accidentally or intentionally, goes up exponentially.

It is crucial that President Obama and the leading nations of the world, including Russia and China, draw the line in the sand on Iran.

Kathleen Troia “K.T.� McFarland served in national security posts in the Nixon, Ford and Reagan administrations. She is a frequent contributor to the FOX Forum and Foxnews.com's "Strategy Room." She also appears weekly in the Foxnews.com video blog "DefCon3."