Washington: The fear that nuclear materials may fall into the hands of Islamic State or other terrorist groups will be a major issue at this week's Nuclear Security Summit in Washington, involving more than 50 countries with the notable exception of Russia.
The biennial event was launched in 2010 at the initiative of US President Barack Obama, who pledged at the start of his term to make nuclear non-proliferation a priority.
Last week's terror attacks in Brussels have given further impetus to efforts to safeguard stockpiles of nuclear material.
The summit will begin on Thursday evening with a working dinner at the White House where Obama and the heads of the respective national delegations "will share their perspectives about the threat of nuclear terrorism", Deputy National Security Adviser Ben Rhodes said.
Russia, the world's other great nuclear power along with the US, is skipping the summit to protest "a certain lack of cooperation during the preliminary stage of working on issues and topics of the summit", Kremlin spokesperson Dmitry Peskov said on Wednesday.
Among the leaders who will attend are Indian Prime Minister Narendra Modi, French President François Hollande, Britain's David Cameron, Turkish President Recep Tayyip Erdogan, Ukraine's Petro Poroshenko, and the president of Kazakhstan, Nursultan Nazarbayev.
Kazakhstan co-chairs with Japan the organisation pushing for implementation of the Comprehensive Nuclear Test Ban Treaty.
When the collapse of the Soviet Union in 1991 left Kazakhstan in possession of the world's fourth-largest nuclear arsenal, the government of the newly-independent nation ordered the immediate dismantlement of the stockpile.
In 2006, Astana ratified the Central Asian Nuclear-Weapon-Free Zone and last year, Kazakhstan became the home of the International Atomic Energy Agency's Low Enriched Uranium Bank, which is meant to ensure a supply of fuel for peaceful nuclear power.