The US warned on Saturday that al-Qaeda has stepped up its hunt for a nuclear bomb, lending urgency to the historic nuclear summit where President Barack Obama wants countries to help lock down the world's atomic materials within four years.
US Secretary of State Hillary Clinton said this will be the largest assembly of world leaders hosted by an American President since the 1945 conference that founded the UN.
The tone for the conference would be set by Obama by meeting with the Prime Ministers of India and Pakistan, the two new nuclear powers.
India will voice its apprehensions over nuclear material falling into the hands of terrorists.
"I expect the summit to focus on nuclear terrorism and proliferation of sensitive nuclear materials and technologies," Singh said in a statement before leaving for Washington.
A communique to be issued at the end of the Nuclear Security Summit wants countries to endorse a pledge to take steps to prevent terrorists and criminal groups from gaining access to atomic weapons.