He wants us to disarm our nuclear capability so that terrorists won't have nukes. Brilliant!
This is my edit: I was wrong about the above. I was distracted momentarily and heard it wrong. Here's what he said verbatim, taken from the transcipt:
And at April's Nuclear Security Summit, we will bring 44 nations together here in Washington, D.C., behind a clear goal: securing all vulnerable nuclear materials around the world in four years so that they never fall into the hands of terrorists.