However, the fresh pact - as revealed by TVNZ this week - has raised plenty of red flags in New Zealand, which has a special constitutional relationship with the Cooks.
The Cook Islands is a Polynesian country of 15 islands wedged between Tonga and Samoa to its west, and French Polynesia to its east, home to around 20,000 people and popular holiday spot for Kiwis.
Another 100,000 people - including former Wallabies coach Dave Rennie - identify as Cook Islanders living in New Zealand.
Cook Islands Prime Minister Mark Brown has confirmed travel to Beijing next week to sign a "comprehensive strategic partnership" with China, telling TVNZ he saw the two nations as "like-minded".
"In terms of economic growth and the prosperity of our peoples, we share those common interests," he said.
The tie-up will see China assist the Pacific nation grow its fisheries, assist with its ferry network, and collaborate on Mr Brown's pet industry: deep sea mining.
Mr Brown said the deal was not similar to a bombshell 2022 announcement by the Solomon Islands that it would partner with China on security, a pact which caught Australia off-guard.
"Our agreement doesn't have any of those aspects in it," he said.
New Zealand's Foreign Minister Winston Peters has signalled alarm with the deal, suggesting his government was blind-sighted.
For 60 years, the Cook Islands has governed in "free association" with New Zealand under a treaty that gives Cook Islanders citizenship of New Zealand, and gives Wellington shared responsibility for foreign affairs and defence.
New Zealand is also the Cook Islands' biggest development partner, giving $US219 million ($A349 million) over the last 15 years: more than double China's aid, and four times the support from Australia.
"We want clarity," Mr Peters told TVNZ.
"We've got constitutional arrangements which require consultation with us ... and dare I say it, China knows that."
A deal is likely to be frowned upon in Canberra and Washington, given western opposition to Chinese influence in the region.
Under Mr Brown's leadership, the Cook Islands government has struck an increasingly independent tone, even exploring to establish its own citizenship and passport.
A spokesman for Mr Peters confirmed "a number of issues on which New Zealand and the Cook Islands do not see eye-to-eye", including the passport proposal and transparency over the China deal.
The government dispatched its top diplomatic bureaucrat, Bede Corry, to Rarotonga for emergency talks over the pact.
New Zealand - which also gives Cook Islanders free movement and access to New Zealand's health system - says that will only be possible through a breakaway via a referendum.
"If he wishes to create a separate Cook Islands passport and citizenship then he is advocating independence from New Zealand," Mr Peters told TVNZ last year.
"Prime Minister Brown needs to make it clear to Cook Islanders that they can have a Cook Islands passport or a New Zealand one ... they cannot have both."
New Zealand wants a continuation of current governing arrangements, with a spokesman for Mr Peters calling the Cook Islands an "integral" part of its family.
Mr Brown will travel to China from February 10-14 to sign the pact, promising further details then.
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