A nuclear security summit in The Hague has ended with 35 nations pledging to incorporate international guidelines on the protection of nuclear materials into law.
They agreed vowed to "realise or exceed" the standards set out in a series of guidelines laid down by the International Atomic Energy Agency to safeguard nuclear materials.
These are the "closest things we have to international standards for nuclear security", said US Energy Secretary Ernest Moniz afterwards.
The summit also agreed to allow experts from the agency to evaluate their security procedures for nuclear material.
New Zealand prime minister John Key said all the countries were aware of their responsibilities and were committed to enhancing nuclear security.
The summit has been overshadowed by the crisis in Ukraine.
The United States, Britain and Japan were among the nations to agree to the deal. Major nuclear powers Russia, China, India and Pakistan were among the 18 countries that did not join the initiative.
Countries that committed to implementing international guidelines also agreed to allow independent experts to "evaluate their security procedures for nuclear material", the NSS said in a statement on Tuesday.
They furthermore pledged to keep the quantities of nuclear material "as low as possible".
Russian President Vladimir Putin did not attend the two-day summit and instead sent his foreign minister, Sergei Lavrov, the BBC reports.
In his closing remarks, American President Barack Obama said 12 countries and two dozen nuclear facilities around the world had now "rid themselves entirely of highly enriched uranium and plutonium.
"We've seen a fundamental shift in our approach to nuclear security, but we still have a lot more work to do to fulfil the ambitious goals we set four years ago to fully secure all nuclear and radiological material, civilian and military, so it can no longer pose a risk," he said.
The BBC says the US president used the final news conference to praise Ukraine's decision at the 2010 to remove all its dangerous materials from its nuclear fuel sites.
"Had that not happened, those dangerous nuclear materials would still be there now and the difficult situation we're dealing with in Ukraine today would involve yet another level of concern," Mr Obama said.
One of the main objectives of the deal is to prevent terrorists from obtaining nuclear material.
Mr Obama hosted the first summit in Washington DC in 2010, a year after he declared nuclear terrorism "one of the greatest threats to international security", the BBC reports. The next summit will be held in the United States in 2016.
The leaders' group at the National Security Summit. Photo: RNZ / Demelza Leslie