New Zealand's defence minister has sympathised with the Trump administration's push for partner countries to lift defence spending, saying Australia and New Zealand are among nations that have been "pretty slack" for decades.

Judith Collins said for too long American taxpayers have had to "carry the burden", and while the United States has not directly asked New Zealand to boost its defence spending, Ms Collins said she understood the broader push from the Five Eyes partner and wanted to lift NZ's spend further.

The White House has demanded Australia lift defence spending by almost $40 billion a year "as soon as possible", as it reviews the keystone AUKUS nuclear-powered submarine pact between the countries.

Ms Collins said since the Berlin Wall fell in 1989, countries including Australia, New Zealand and some throughout Western Europe had "sat back". 

"People thought, 'well, there we go, peace is broken out, no one's going to be stupid' and then Putin came along and all of a sudden, things changed," she said in an interview with ABC News in Wellington.

"Everyone's been pretty slack and the Americans have been carrying us.

"While we've been going ahead and building our welfare states and making sure we have free health care and education and everything else, their people have actually had to fund a lot of the defence of the democratic world.

"So, I have a certain sympathy to everyone doing a little bit more."

New Zealand currently spends about 1 per cent of its GDP on defence, and earlier this year promised to lift that to 2 per cent within eight years.

But Ms Collins — who is a conservative politician from New Zealand's National Party — insisted she was "looking to do more than that when we can", although she did not indicate how much more.

For comparison, Australia's current defence spending is about 2 per cent of GDP and is forecast to hit 2.3 per cent in the same timeframe.

But the actual dollar figure Australia is set to spend will equal tens of billions of dollars more than New Zealand because it has a larger economy.

Regardless, both figures are much lower than the 3.5 per cent the Trump administration has been loudly calling on Australia to reach.

The government has defended against repeated calls to lift defence spending, including from the Dutch defence chief last month, with Prime Minister Anthony Albanese repeating again over the weekend that the government would not pursue an arbitrary target.

Live firing drills an 'absolute reminder'

Speaking with ABC News, Ms Collins was also critical of China's recent behaviour in the Indo-Pacific region, including its live firing drills in the Tasman Sea in February, which caused commercial flights to change course.

She said it was an "absolute reminder" to Australia and New Zealand of how close China is and the rising strategic competition in the region, warning that competition was already leading to an increase in foreign interference and "influence" of Pacific policing forces.

Ms Collins was also particularly critical of China's recent deal with the Cook Islands on trade and the "seabed minerals sector", which Wellington felt it should have been aware of ahead of time.

"We think was it was certainly unusual, it wasn't expected, and it is a wake-up call again, for New Zealand," she said.

She explained the region's rich resources made it an area for great competition, but was mindful Australia and New Zealand had relatively small populations with which to defend it.

"We have the ninth largest exclusive economic zone in the world with massive resources, particularly on our seabed," she said.

"We are countries with enormous resources and actually not that much in terms of defence compared to what other nations might have."

On top of that, she acknowledged her defence force had been struggling to attract and retain enough personnel, although those numbers have recently improved.

NZ not yet invited to join second stage of AUKUS

While the Trans-Tasman allies have put a big focus on increasing the interoperability of their defence forces in recent months, it is still not clear if New Zealand will join the second stage of the AUKUS security pact.

While Ms Collins talked up the benefits of AUKUS as an opportunity for peace, she said New Zealand had still not been invited to join Pillar Two, which largely involves the sharing of technology.

"Obviously a lot of work's going on behind the scenes, but none of it has got to cabinet yet, so there's no decision yet."

The US administration is currently reviewing the AUKUS commitment to provide Australia with nuclear-powered submarines in partnership with Britain.