Scott Morrison made his first call on the morning he announced the historic AUKUS deal to Jacinda Ardern, who soon made it clear nuclear submarines would not be welcome in New Zealand waters.
Australia, the US, and Britain on Thursday morning formed a new alliance to beef up security in the Asia Pacific to counter the rising threat of China.
At least eight nuclear-powered submarines are expected to be delivered to Australia under the deal.
Ms Ardern was the first international leader the Australian prime minister called on Wednesday, hoping New Zealand could alleviate concerns from South Pacific countries impacted by previous nuclear testing, The Australian reported.
The New Zealand leader reiterated her country's firm anti-nuclear stance, but stressed ties with the three countries remained strong.
Scott Morrison (pictured, left) called Prime Minister Jacinda Ardern (right) before announcing the historic AUKUS deal - who made it clear nuclear submarines would not be welcome in New Zealand's waters
The pact does not make the design of Australia's new submarines clear, but they will be based on previous US and UK designs (pictured, a cross-section of Britain's Astute-class nuclear attack subs, which is likely to mirror the new vessels)
'New Zealand's position in relation to the prohibition of nuclear powered vessels in our waters remains unchanged,' she said just minutes after the announcement.
'The centrepiece of it is nuclear powered submarines and all parties are very well versed in understanding our position on nuclear powered vessels and weapons.
'They couldn't come into our internal waters… our legislation says no vessel wholly or fully powered by nuclear energy can enter our internal waters.
'That is a position held across parties for a long period of time.'
After phoning Ms Ardern, Mr Morrison spoke to Indian Prime Minister Narendra Modi along with the leader of Japan Yoshihide Suga.
Meanwhile, Defence Minister Peter Dutton and Foreign Affairs Minister Marise Payne spoke to Indonesia's corresponding ministers on Wednesday while other ASEAN leaders were addressed on Thursday.
Scott Morrison and Jacinda Ardern (pictured in February 2020) say their nations will continues to cooperate on regional security
Ms Ardern insisted New Zealand had no interest in being part of the new AUKUS triumvirate and saw it as less important than the Five Eyes intelligence sharing arrangement, which was formed in 1941.
'[AUKUS] isn't at the level of existing partnership with UK, Canada, the US, Australia and Canada,' she said.
Ms Ardern said she was informed about Australia's partnership with the US and Britain at the same time as Scott Morrison's cabinet, but wasn't invited.
'No we weren't approached, nor would I expect us to be,' Ms Ardern said.
She said it was 'very clear' New Zealand wouldn't want to belong to the alliance because of its promotion of nuclear-powered submarines.
At least eight nuclear-powered submarines are expected to be delivered to Australia under the deal (pictured, The Royal Australian Navy's HMAS Waller - which is diesel-electric)
Australia's new nuclear submarines, which are to be built in Adelaide as part of the AUKUS alliance with the UK and US, will not be welcome in New Zealand (pictured, a guided-missile submarine in the Strait of Hormuz)
The New Zealand public has long supported an official anti-nuclear stance.
The American navy's nuclear-powered guided missile cruiser USS Truxtun came under heavy water-based protests from civilians when it visited New Zealand in 1982.
The nation's government made world headlines in the 1980s for denying a visit by US destroyer USS Buchanan in 1985 after the US refused to deny that the warship had nuclear capability.
As part of the AUKUS arrangement, Australia's two most important allies will help it build nuclear-powered submarines for the first time.
'It is the first time this technology has ever been made available to Australia. This is a one-off, as the President in Washington has made very clear. This is a very special arrangement,' Mr Morrison said.
The American navy's nuclear-powered guided missile cruiser USS Truxtun (pictured) came under heavy water-based protests from civilians when it visited New Zealand in 1982
The prime minister was joined virtually for the announcement by US President Joe Biden and British Prime Minister Boris Johnson in a historic joint press conference.
None of the leaders mentioned China by name but the West is increasingly concerned about Beijing's growing assertiveness and huge military build-up.
Ms Ardern said New Zealand wants 'peace' in the region but does support 'more engagement' by the UK and US.
'We want peace and we want stability in our region and a rules based order preserved and that is position we will come at on all these issues.'
Ms Ardern challenged the Kiwi opposition to come out and support her statements, given it had spoken in support of AUKUS.
China has vastly built up its military in the past few years and now possesses six Shang-class nuclear powered attack submarines, equipped with torpedoes and cruise missiles. This graphic shows a comparison of the two militaries
Why is Australia acquiring nuclear-powered subs?
Why nuclear submarines?
Nuclear submarines are powered by nuclear reactors which produce heat that creates high-pressured steam to spin turbines and power the boat's propeller.
They can run for about 20 years before needing to refuel, meaning food supplies are the only limit on time at sea.
The boats are also very quiet, making it harder for enemies to detect them and can travel at top speed - about 40kmh - for longer than diesel-powered subs.
The first nuclear submarines were put to sea by the United States in the 1950s. They are now also in use by Russia, France, the United Kingdom, China, and India.
A senior US defence official told reporters in Washington DC: 'This will give Australia the capability for their submarines to basically deploy for a longer period, they're quieter, they're much more capable.
'They will allow us to sustain and to improve deterrence across the Indo-Pacific.'
Zack Cooper, a senior fellow with the American Enterprise Institute, said nuclear submarines would hugely boost Australia's military capability.
'They are going to be much, much more capable in the large, expansive ocean that is Australia has to deal with,' he told the ABC.
Will Australia have nuclear weapons?
Scott Morrison made it clear that the nuclear-power submarines will not have nuclear missiles on board.
Australia has never produced nuclear weapons and signed the Treaty on the Non-Proliferation of Nuclear Weapons in 1973 which prevents non-nuclear states which don't already have them from developing nuclear weapons.
Mr Morrison also said the Australia has no plans to build nuclear power stations which are widely used around the world.
'But let me be clear, Australia is not seeking to acquire nuclear weapons or establish a civil nuclear capability,' he said.
'And we will continue to meet all our nuclear non-proliferation obligations.'
Australia needs to replace its six ageing Collins-class submarines.
In 2016 it signed a deal with French Company Naval Group to build 12 diesel-electric attack subs - but the parties were in dispute over the amount of building that would be done in Australia.
That deal has now been torn up in favour of nuclear powered subs aided by the US and UK who will provide the technology to Australia.
The West is becoming increasingly concerned about the growing assertiveness of China in the Indo-Pacific region where it has made huge territorial claims in the South and East China seas, clashed with Indian troops and repeatedly flown planes over Taiwan.
Mr Morrison wants Australia to have serious defence capability to deter China from encroaching in the Pacific and long-range nuclear submarines are just the ticket.
China has vastly built up its military in the past few years and now possesses six Shang-class nuclear powered attack submarines, equipped with torpedoes and cruise missiles.