North Korean leader Kim Jong-un is unpredictable and his treatment of people is abhorrent and barbaric, Prime Minister John Key says.

LISTEN ABOVE: Newstalk ZB political reporter Frances Cook speaks with Mike Hosking

Concerns over disputes in the South China Sea are expected to take a back seat as leaders discuss the challenges to regional security posed by the dictator's latest series of nuclear tests when the East Asia Summit opens in Vientiane, Laos on Thursday.

The Prime Minister has already discussed the erratic behaviour with Australian Prime Minister Malcolm Turnbull in a bilateral meeting on Wednesday, where the two reaffirmed they were still "BFFs" after Mr Turnbull tweeted earlier in the week that no countries were closer than Australia and Britain.

"New Zealand media were offended that you might not love me as much as Theresa May, I was trying to say 'oh for God's sake we're BFF's forever," Mr Key joked, to which Mr Turnbull responded "yeah we are, that's absolutely right".

The pair briefly discussed the G20 Summit, protectionism in trade and counter terrorism, but it's conversations surrounding Kim Jong-un, who Mr Key described as a "lone wolf", and tensions on the Korean peninsula that are expected to carry into the East Asia Summit.

"His behaviour and the way he's treating people, if you believe the media reporting of that, is not only abhorrent but well it's barbaric and a sign of a person that is extremely unpredictable and difficult to read," Mr Key said.

He described the meeting as a chance to go over some topics for a private dinner he and Mr Turnbull will hold in Pohnpei, Micronesia on the weekend when they both attend the Pacific Islands Forum.

Earlier on Wednesday Mr Key met with Myanmar State Counsellor Aung San Suu Kyi and Singaporean Prime Minister Lee Hsien Loong.

"(Myanmar) is particularly interested in working with New Zealand around development of their food sector, in particular dairy, they see real opportunities there," he said.

Mr Key has more bilateral meetings scheduled for Thursday, including with Russian Prime Minister Dmitry Medvedev where Mr Key will again raise his predecessor Helen Clark's bid to become the next United Nations Secretary- General.

Russia has already indicated that it would prefer an Eastern European candidate for the job, but Mr Key remains hopeful Miss Clark could still be a contender if the permanent five members cannot agree.

"In fairness to the Russians they've been quite upfront about their position, they genuinely believe it's an Eastern European person's chance ... I'm not sure we're really going to change Dmitry Medvedev's view or the Russian perspective but we are going to put on the record absolutely that we think she's the right person and that she should be considered."

But he said it would be "game on" if the Eastern European candidates dropped out.

There are no plans for a sit down meeting between Mr Key and US President Barack Obama, but Mr Key indicated he also hopes to speak to President Obama about Miss Clark, who ranked seventh in the latest straw poll last month.

"I've had some discussions with President Obama on the phone some weeks ago about that issue. I think he personally is very sympathetic towards Helen Clark but look, let's wait and see," he said.

The duo are also expected to discuss the Trans-Pacific Partnership, which Obama hopes to see pass before his time as president ends.
Economic matters are of equal importance to Mr Key, given New Zealand's integration into the Asian markets.

Mr Key kicked off his itinerary meeting Laotian students who have received ASEAN scholarships to study in New Zealand next year.