United States President Barack Obama has hailed the success of the summit on nuclear security, saying it has made the world a safer place.
Leaders of 47 countries, including New Zealand, pledged in Washington to safeguard nuclear stocks and keep material out of terrorists' hands within four years.
Mr Obama says the possibility of terrorists getting hold of nuclear material is the greatest threat to world security, but warned there is still much hard work ahead to achieve the plan.
He said the summit had made "unprecedented progress in confronting the greatest threat to global security."
A draft communique to be issued at the summit also promises greater efforts to block groups such as al Qaeda from obtaining the building blocks for nuclear weapons.
The BBC reports officials are delighted that some deals that have been years in the making have come to fruition in Washington.
They include Russia and the US signing an agreement to dispose of 68 tonnes of surplus weapons-grade plutonium, said to be enough to make 17,000 nuclear warheads.
American officials said the plutonium would be used as fuel in civilian reactors to generate electricity.
The US will provide $US400 million of the funding for the disposal of Russia's plutonium, which Moscow estimates will cost up to $US2.5 billion.
Several other countries - including Mexico, Chile and Ukraine - had earlier agreed to give up their stocks of highly-enriched uranium.
The United States, Canada and Mexico have agreed to work together with the International Atomic Energy Agency (IAEA) to convert Mexico's research reactor from the use of highly enriched uranium to low enriched uranium fuel.
New Zealand Prime Minister John Key says world leaders have agreed to expand the role of the IAEA.
Mr Key says it was agreed that the United Nations nuclear agency needs to move from being a nuclear safety agency to one that is actively involved in safeguarding nuclear materials and technology.
The Prime Minister believes the change in focus is an important development in nuclear security.