VOICED: Washington under high security as Nuclear Summit begins

The US Capitol is on lockdown as leaders from 46 nations gather for a summit focused on nuclear security. The event, chaired by the US President, aims to prevent nuclear materials from falling into terrorist hands. Local areas are heavily secured, affecting residents and commuters. The President seeks commitments to secure nuclear stockpiles and support for sanctions against Iran. A key meeting between the US and China is closely watched.

What commitments is the American President hoping to secure from other nations?

What is the significance of the bilateral meeting between Obama and Hu Jintao?