Defence Minister Gerry Brownlee has accused North Korea of having "evil intent" but will not go as far as saying New Zealand will back any US action against the country.

North Korea last night warned Australia of a possible nuclear strike if it persisted in "blindly and zealously toeing the US line".

Pyongyang's blunt statement was in response to comments by Australia's Foreign Minister Julie Bishop earlier this week, when she said North Korea's nuclear programme posed a "serious threat" to Australia unless it was stopped by the international community.

Asked on TVNZ's Q+A this morning whether New Zealand would side with the US in any action against North Korea, Brownlee said that would be decided if that point was reached.

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He would not be drawn on whether New Zealand agreed with the US position that China should be doing more to deal with North Korea.

But he emphasised sanctions and ongoing diplomacy should be the first option in resolving tensions in the Korean Peninsula.

"The difficulty is here you have got a leader that people know very little about [Kim Jong-Un's regime]," he said.

"But you would assume that underneath him there is a very big machinery of people who have equally evil intent.

"And so you've got to make sure that you think about the millions of North Koreans who are suffering under that regime."

Brownlee did not shy away from blaming North Korea for the tension in the region.

"What I would say is it's North Korea that is sending the missiles into the Sea of Japan and making the various outrageous threats including the threats overnight to Australia."

He also noted that US President Donald Trump, like his predecessor Barack Obama, had made it clear there was an expectation that the rest of the world would assist in getting rid of oppressive regimes - not only in North Korea but also in Syria.

New Zealand's Defence White Paper, released last year, made little reference to the Korean Peninsula or the South China Sea disputes.

Brownlee said today New Zealand was still closely monitoring these disputes, but that the issues in the South China Sea were "for the countries most affected".

He rejected the suggestion New Zealand had "pulled its punches" on the South China Sea, saying he had "never backed away from discussing those things with Chinese military people when I've had the opportunity".

"And [I have] made it clear our position that we think the freedom of navigation through those areas is important, that the recognition of the territorial sea is important, and the arrangements of the countries who have those claims needs to be settled on a one-to-one basis."