United States President Barack Obama has referenced comments made by Prime Minister John Key in his closing address to leaders at the Nuclear Security Summit in South Korea.

In an unscripted four minute address yesterday Mr Key urged other leaders at the summit to take whatever steps were necessary to secure nuclear materials to avoid a terrorist attack.

"So in the event a terrorist attack takes place, we as leaders will be called to account to make sure we did everything we could. We've identified the issue but have we actually done everything to protect our citizens from this?

"I believe that one day the risk of a terrorist attack is so real that the actions we take at this summit will be challenged. If we don't step up to the mark we will be found wanting and that's not a position that any one of the 53 of us would want to be called to account for.''


Mr Key also said a nuclear terrorist attack would have more of an impact than 9/11 on every country in the world.

President Barack Obama later referred to Mr Key's statement when he was giving his own closing remarks.

He spoke about Mr Key's call for the countries to take the threat of nuclear terrorism seriously and the impact that such a catastrophic event as a nuclear terrorist attack would have on the world.

He noted that Mr Key had referenced it in the context of the September 11 attacks on the Trade Towers.

The only other leader Obama referred to specifically in his closing was the Italian Prime Minister.

Mr Key had earlier said he was encouraged by the apparent commitment to the issue from leaders with significant nuclear stores but urged the leaders to be ambitious in their commitments.

He told the other leaders he had a different perspective from theirs because New Zealand was a small, isolated country with a small population.

"If you add on top of that we are one of the few countries in the world that has passed legislation to be nuclear-free for 25 years. So you might ask why we are here."


He said his statement was intended to provide a different perspective from that of the major nuclear powers.

"It was also to try to encourage those countries to think about the 100-plus countries that aren't represented around that table.''

Mr Key said his statement also drew favourable mentions from Australia's Prime Minister, Julia Gillard, and the Netherlands.

Mr Key also had a lengthy discussion with Barack Obama yesterday, during which a spokeswoman said they canvassed numerous issues including Trans Pacific Partnership talks.

Mr Key said Obama was confident there was good progress in those talks.

The summit wound up last night after the leaders issued a communique with future goals.

Several more countries, including Italy, pledged to eliminate their stocks of fissile material and there was a joint agreement between the US, France, Belgium and the Netherlands to produce medical radioactive isotopes without using highly enriched uranium.

New Zealand has given $500,000 for nuclear material in Uzbekistan to be moved to Russia for disposal.

After the summit, Mr Key said New Zealand had given about $6 million towards disposal of nuclear material in other countries since 2006.