For two countries meant to have one of the most close-knit relationships in the world, it's an extraordinary stoush.
This week, New Zealand's sometimes outspoken Foreign Minister Winston Peters issued a sharp rebuke to the Cook Islands, a sprawling Pacific archipelago that has been in a state of "free association" with Wellington for almost six decades.
Two disputes have broken out between the two countries in less than six weeks.
This week's disagreement centres on the Cook Islands' push to establish much closer ties with China without fully looping in New Zealand — something Mr Peters has suggested is in clear breach of its obligations to Wellington under its special relationship.
The second concerns more fundamental and knotty questions about exactly how the Cook Islands can assert its own separate national identity while maintaining its unique ties with New Zealand and the benefits that flow from that.
Mr Peters has also become embroiled in a separate dispute with Kiribati, announcing last month that he'd review New Zealand's aid program to the Pacific nation after being repeatedly snubbed by its sometimes reclusive president, Taneti Maamau.
Incidents like this are quite rare in the Pacific, where quiet diplomacy is usually preferred, and senior politicians tend to solve disputes in private rather than public.
So what is behind these recent conflicts?
What are the prospects for resolution? And what might happen next?
China deal sparks tension between Cook Islands and New Zealand
The most recent dispute is over a document with a rather wieldy title: the "China-Cook Islands Joint Action Plan for Comprehensive Strategic Partnership".
Cook Islands Prime Minister Mark Brown is travelling to China at the weekend to sign the agreement, promising that it will help "expand economic opportunities" and draw assistance from Beijing across a host of fields, from infrastructure to shipping and green energy.
It's hardly the first agreement China has signed with a Pacific Island nation, but the pact has provoked considerable unease in Wellington.
Mr Peters made it clear to New Zealand media outlet 1News that he was unhappy Cook Islands had not shared the agreement with Wellington, suggesting it was a breach of the free association agreement, which will mark its 60th anniversary later this year.
The foreign minister also suggested that China was deliberately trying to drive a wedge between New Zealand and Cook Islands.
"We've got past arrangements, constitutional arrangements, which require consultation with us and, dare I say, China knows that," he said.
What exactly is the arrangement between Cook Islands and New Zealand?
The "constitutional arrangements" the minister was talking about is the rather unique free association agreement between both countries, which hands residents of Cook Islands citizenship of New Zealand and a NZ passport.
The pact stresses Cook Islands has the capacity to enter into treaties and international agreements in its own right.
But the Cook Islands has also agreed that both countries will "consult regularly" on foreign policy to try and formulate "common policies".
Under the agreement, both countries have also agreed to "cooperate and assist each other" on defence and national security issues and advise each other of "any risks that may affect either or both signatories".
Mr Brown, the Cook Islands leader, insisted in the interview with 1News that the agreement with China had nothing to do with security or defence issues — perhaps suggesting that it didn't trigger any of its obligations to New Zealand under the pact.
"I know that New Zealand and Australia's concerns centre around security matters and I guess they bring up the Solomon Islands signing an agreement which allows [Chinese] policing," he said.
"Our agreement doesn't have any of those aspects in it."
But New Zealand views the document through a markedly different lens.
Much like Australia, New Zealand believes China poses profound strategic and security challenges in the Pacific — and fears that Beijing is intent on securing a military beachhead in the region.
In other words: Mr Brown is going to face a struggle convincing Wellington that a broad new agreement with an emerging great power — which also happens to be NZ's chief strategic adversary in the region — can be airily waved through as an unremarkable development pact.
After the story first broke this week, a spokesperson for the foreign minister later said NZ was concerned by the "lack of transparency by the Cook Islands in respect of policies and partnerships with other countries" adding the agreement could have "significant security implications for the Cook Islands, New Zealand and the wider Pacific family".
"We have also emphasised that we would expect the New Zealand government to be fully consulted on any major international agreements that the Cook Islands plans to enter into that have major strategic and security implications," they said.
At this stage, however, there's no sign of Mr Brown backing down.
The prime minister will take off for China today, and everyone is expecting the new agreement to be signed in Beijing in the coming few days.
"There is no need for New Zealand to sit in the room with us while we are going through our comprehensive agreement with China," Mr Brown told RNZ on Friday.
"We have advised them on the matter, but as far as being consulted and to the level of detail that they were requiring, I think that's not a requirement."
Victoria University of Wellington professor of comparative politics Jon Fraenkel told the ABC it was "not at all clear" whether the Cook Islands had in fact breached its obligations to New Zealand with the China pact because the wording in the documents they've signed was so broad.
"The agreements between the two countries are ambiguous and ill-defined," he said.
Cook Islands' passport push meets with stiff resistance from New Zealand
The China dispute, with all of its fraught questions around sovereignty and constitutional obligations, hasn't cropped up in isolation.
It's come at a time when Mr Brown is pressing to up-end some of the assumptions that have underpinned the status quo with New Zealand for decades.
The prime minister's most contentious idea was for Cook Islands to issue its own passport, rather than simply using the passports of its former colonial master — a proposal he dumped on Friday.
For months, Mr Brown had insisted Cook Island residents wanted the passport to assert their own unique Pacific identity and insisted he could issue the document without undermining the constitutional arrangement between the two countries.
But Mr Peters was adamant that would not happen, saying issuing standalone passports would essentially herald full and complete independence for Cook Islands, and lead to a rupture with New Zealand.
"A Cook Islands passport would raise fundamental questions for our shared constitutional relationship and shared citizenship," he said in December.
He said if Mr Brown wanted the passport, he would need to pass the proposal at a referendum.
NZ also warned that if Cook Islanders did take up their own passport, they'd be stripped of the benefits of the status quo — including automatic NZ citizenship, residency and essential services.
"Such a referendum would allow the Cook Islands people to carefully weigh up whether they prefer the status quo, with their access to New Zealand citizenship and passports, or full independence," Mr Peters said.
That prospect stirred plenty of unease in Cook Islands, with some residents taking to social media to criticise Mr Brown and other locals signalling they'd hold a protest this weekend.
On Friday, the prime minister backed down, telling local media that he'd taken the passport proposal "off the table at the moment" because he didn't want to risk stripping Cook Islands residents of their rights in New Zealand.
He insisted the relationship with Wellington was still "very good" but his answer suggested bad blood between the two sides still lingered.
"New Zealand has bared its teeth. New Zealand government has said that they are willing to go to change the law in New Zealand to punish Cook Islanders," he said.
"So we're not going to have that."
Director of the Wellington-based Centre for Strategic Studies, David Capie, told the ABC that the two disputes suggested "real tension between PM Brown's ambitions and the scope of the free association relationship with New Zealand".
"Trust and consultation are absolutely central to the free association concept and shared citizenship", he said.
"But New Zealand clearly feels the Cook Islands government is not living up to its side of the bargain."
High stakes as New Zealand responds to Kiribati snub
Cook Islands might not be the only Pacific country in this category.
In January, Mr Peters's frustration with the remote island nation of Kiribati also spilled over after his attempts to secure a meeting with its president, Taneti Maamau, were rejected for a third time.
The foreign minister responded by announcing he'd review New Zealand's substantial aid program with Kiribati — worth some $25 million a year — saying without high-level meetings, he couldn't properly account for how the money was being spent.
"A lack of political-level contact makes it very difficult for us to agree joint priorities for our development program, and to ensure that it is well-targeted and delivers good value for money," he said.
Again, this isn't happening in isolation.
Like Australia, New Zealand has been worried about the authoritarian turn taken by Kiribati under President Maamau, criticising the way his government has targeted the country's judiciary.
They were frustrated when Mr Maamau withdrew Kiribati from the Pacific Islands Forum — before later returning to the fold — in the wake of the Micronesian "PIF split" in 2021.
Both countries have also struggled to gain diplomatic access to the country — although Mr Maamau did meet with Australian Foreign Minister Penny Wong in Kiribati two years ago.
It's not yet clear if Mr Peters's decision to play hardball with both Kiribati and Cook Islands signals a shift in New Zealand's broader Pacific strategy, with an increasing appetite to deploy sticks as well as carrots.
But as China continues to press its weight in the Pacific, the strategic stakes have never been higher.
Mr Peters may have decided that the time for low-risk diplomacy has well and truly passed.
