Addressing the Nuclear Security Summit here, Obama said the world would need "a new manner of thinking and action" to deal with the real problem facing the world peace and stability.

"Terrorist networks such as al-Qaeda have tried to acquire the material for a nuclear weapon. And if they ever succeeded, they would surely use it.
"Were they to do so, it would be a catastrophe for the world, causing extraordinary loss of life and striking a major blow to global peace and stability," he told a gathering of leaders from 47 countries, including Prime Minister Manmohan Singh, assembled to discuss ways to prevent terrorists gaining access to nuclear material and know-how.
He said it was increasingly clear that the danger of nuclear terrorism is "one of the greatest threats to global security, to our collective security."

Obama referred to his speech in Prague last year where he had called for a new international effort to secure all vulnerable nuclear materials, around the world, in four years.

"We have the opportunity as individual nations to take specific and concrete actions to secure the nuclear materials in our countries and to prevent illicit trafficking and smuggling. That will be our focus this morning," Obama said.
The Summit is being held against the backdrop of fears that nuclear material and arsenal in Pakistan were not secure.

"We have the opportunity to strengthen the International Atomic Energy Agency, the IAEA, with the resources and authorities it needs to meet its responsibilities, and that will be our focus at our working lunch."And we have the opportunity as an international community to deepen our cooperation and to strengthen the institutions and partnerships that help prevent nuclear materials from ever falling into the hands of terrorists, and that will be our focus this afternoon," Obama said.

He told the world leaders that "today is an opportunity" not only to make pledges, but also to make real progress on the security of their people."All this, in turn, requires something else, which is something more fundamental. It will require a new mindset, that we summon the will as nations and as partners to do what this moment in history demands," Obama said.

"For the sake of our common security, for the sake of our survival, we cannot drift. We need a new manner of thinking and action," he said, adding "That is the challenge before us."

The two-day Summit is focused on dangers posed by clandestine proliferation and illicit trafficking of nuclear material and the possibility of terrorists acquiring atomic material.
An outcome document is expected to be issued at the end of the Summit that will outline the national responsibilities of countries to protect their nuclear material and weapons while adhering to international legal instruments and norms.