What Obama's nuclear summit hopes to achieve

The summit of world leaders from 47 countries, including Prime Minister Manmohan Singh, will open with a warning by Obama that terror groups like Al Qaeda have aspirations to arm themselves with nuclear weapons.

The gathering of presidents and prime ministers has been described as the largest gathering of world leaders organised by the US in more than five decades.

The summit would be heralded by Obama hosting a working dinner for the heads of delegations, but US officials said sweeping or bold new initiatives to halt nuclear proliferation were not expected.

"This dinner will be dedicated to addressing the threat of nuclear terrorism," Ben Rhodes, deputy national security advisor for strategic communications, told reporters during a teleconference.

Obama has already sounded the keynote for the conference by warning that "terror outfits like Al Qaeda are in the process of securing nuclear weapons or other weapons of mass destruction and would have no compunction at using them."

He set this tone for the summit during his meeting with Prime Minister Singh last night India time. Obama has set a goal of ensuring all fissile material worldwide are secured from theft or diversion within four years.

On the table would also be major strategies to stop Iran's perceived attempts to build nuclear weapons in violation of the Nuclear Non-Proliferation Treaty and North Korea's nuke weapon stockpile and exports of nuclear material weapons and technology.

Before the working dinner, Obama will formally welcome each of these leaders to the summit.

"We believe that this summit is necessary to galvanise the kind of collective action that's necessary to deal with what really would be the highest consequence threat to the American people and to global security as it relates to the ability of terrorists to acquire a nuclear weapon and use one in one of our cities or any city around the world."

"This would obviously have devastating consequences both in terms of the immediate destruction and loss of life, but also implications for the global security environment after an active nuclear terrorism," he said.

"So tomorrow night, to forge a consensus view about the nature of this threat, the president will be leading a discussion with the heads of the delegations about their perceptions of the threat and, of course, what needs to be done to confront it," Rhodes said.