China has aimed its sights at Australia and New Zealand, accusing their prime ministers of making "groundless accusations" and "grossly interfering in its internal affairs".

It urged Jacinda Ardern and Scott Morrison to "stop making irresponsible remarks and act in ways that are conducive to bilateral relations and regional peace and stability, rather than the opposite".

The pair met in Queenstown for the annual trans-Tasman leaders' dialogue culminating in a strong united front, including on China, laid out in a joint statement and reinforced in comments to media.

"New Zealand and Australia stand together in facing a challenging global environment," the introduction to the section titled Indo-Pacific and Global security reads.

They "reiterated their shared commitment to support an Indo-Pacific region of sovereign, resilient and prosperous states, with robust regional institutions and strong respect for international rules and norms, and where sovereign states can pursue their interests free from coercion".

Australia and New Zealand "committed to continue their close co-ordination and cooperation, as allies and partners, on current and emerging economic, security and environmental challenges in the Indo-Pacific region".

They directly referred to a number of live issues, expressing concern ranging from the South China Sea to the Uyghur people in Xinjiang.

On South China Sea: "Serious concern over developments ... including the continued militarisation of disputed features and an intensification of destabilising activities at sea."

On Hong Kong: "Deep concern over developments that limit the rights and freedoms of the people of Hong Kong and undermine the high degree of autonomy China guaranteed Hong Kong until 2047 under the Sino-British Joint Declaration."

On the Uyghur minority: "Grave concerns about the human rights situation in the Xinjiang Uyghur Autonomous Region."

They called "upon China to respect the human rights of the Uyghur people and other Muslim minorities and to grant the United Nations and other independent observers meaningful and unfettered access to the region".

Speaking to the media after their formal talks on Monday, Ardern and Morrison pushed back on accusations the relationship's been compromised by New Zealand's position on China. Both argued they took a principled stand and were willing to call it out when each deemed fit, regardless of trade or economic consequences.

Foreign Ministry spokesperson Wang Wenbin said China had "taken note of and [is deeply concerned over the relevant statement".]

"The leaders of Australia and New Zealand [have made] irresponsible remarks on China's internal affairs relating to Hong Kong and Xinjiang as well as the South China Sea issue," he said.

"At present, the situation in the South China Sea is generally stable.

"China firmly upholds its territorial sovereignty and maritime rights and interests", Wang said, "at the same time, China is willing to properly handle maritime differences with relevant countries through consultation and negotiation to jointly safeguard peace and tranquility in the region".

"There is never any problem with the freedom of navigation and overflight in the South China Sea.

"We firmly oppose any groundless accusations against China under the pretext of the South China Sea issue."

It would not "waiver in its resolve and will reject any external interference in China's internal affairs", he said, including Hong Kong and the Uyghurs.

"Xinjiang-related issues are about counter-violence, anti-separatism and de-radicalization, rather than human rights, ethnicity or religion ... the rights and interests of people of all ethnic groups, including the Uyghurs, have been fully protected."

ANZAC allies working 'to uphold sovereignty in an era of increasing strategic competition'

The joint statement was littered with references to trans-Tasman solidarity within the volatile global setting.

In pursuit of an "Indo-Pacific region ... where sovereign states can pursue their interests free from coercion", New Zealand and Australia committed to "continue their close coordination and cooperation, as allies and partners, on current and emerging economic, security and environmental challenges".

They "agreed to continue working collaboratively, bilaterally, and with our partners in the Indo-Pacific region, to uphold sovereignty in an era of increasing strategic competition".

Morrison had referred directly to this "strategic competition" in response to questions from reporters - the power battle between China and the United States.

"That is a self evident fact - but I would say that our shared view would be that such strategic competition doesn't need to lead to increased likelihood of conflict, or other pressures, whether they be coercion of any nature or interference, that is not necessary."

Of course the world was uncertain, with "risks of conflict and tension", he said.

"Our efforts are designed to mitigate that, to calibrate against that, and to ensure that we're working together for a more peaceful Indo-Pacific.

The two countries acknowledged the "realities of strategic competition" but did "not accept as any foregone conclusion where that competition may lead to", Morrison said.

He had been asked about the prospect of armed conflict with China, in light of recent comments from his Defence Minister Peter Dutton. There were "many ... who try to divide Australia and New Zealand, all over the place ... they will not succeed," Morrison declared, without naming names.

"The ANZUS arrangements are fairly clear" was his response when asked if he'd expect New Zealand would back its traditional ally if it came to a military showdown with China.

In turn, China spokesperson Wang said Australia and New Zealand should be "conducive to peace and stability in the Asia Pacific, instead of targeting or damaging the interests of third parties, and much less forming enclosed small clique with ideology as the yardstick".

"It's not justifiable for relevant countries to say and do wrong things on issues bearing on the sovereignty and security of a third country, or interfere in its internal affairs under the guise of human rights.

"We once again urge relevant parties to stop making irresponsible remarks and act in ways that are conducive to bilateral relations and regional peace and stability, rather than the opposite," he said.

It wasn't all sweet and light from the two Prime Ministers though. Frustrations flared when the topic of 501 deportations came up.

Ardern and Morrison were also robustly questioned though about cracks - real or imagined - in the relationship.

She visibly bristled at a question from an Australian journalist: "Are you concerned that New Zealand relies too heavily on Australia and others for defence and intelligence sharing and is that why you appear to be cosying up to China?".

"If I had the ability, I would ask for some examples or evidence of the claim that you've made," was the curt response.

"But you've already heard me speak directly and strongly to refute the assertion that we are doing anything other than maintaining a very principled position on human rights issues, on trade issues as they relate to China."

Ardern pointed out there was "very little difference in many of the messages that we've been sending relative to Australia", rejecting "any suggestion that we don't carry and deliver on our behalf and towards the international community".

"In my very strong view, we carry responsibility for ourselves to ensure adequate investment in our defence forces, and equally that we carry our weight as a member of the intelligence insecurity community".

Morrison said he shared Ardern's view.

"We each have different jobs to do, we do each have different capabilities that we bring, it's our job as prime ministers to ensure that comes together ... for the security of our own nations, our own national interests, but also in the broader family role that we have across the Pacific."