North Korea is likely to dominate talks at the East Asia Summit being held in Laos.
Prime Minister John Key is in the Laos capital Vientiane for the talks and a series of meetings with world leaders.
The United Nations has condemned North Korea's latest round of ballistic missile launches.
Mr Key said those launches would be a big focus of the discussions, but they would also include what he called the unpredictability of the North Korean leader, Kim Jong Un.
"I mean that's really the challenge here, this is someone that isn't strongly tied into the rest of the world, acts somewhat as a lone wolf, but is out there testing on a regular basis now bigger, and more powerful, nuclear capability, and so that will be an issue for regional security and stability."
Many of the leaders attending the East Asia Summit have come from the G20 meeting in China, and Mr Key will be seeking an update on what went on there.
He has met with the Australian Prime Minister, Malcolm Turnbull, among others on Wednesday evening, and hoped to have an informal discussion with the US President, Barack Obama, either late tonight or tomorrow during the summit.
Tomorrow he will attend the formal East Asia Summit and also hold talks with the Prime Minister of Laos, the President of the Philippines, and the Russian Prime Minister.
Late tomorrow night Mr Key will fly to Pohnpei in the Federated States of Micronesia for the Pacific Islands Forum.