The Prime Minister is calling on the United States to play a larger role in Asia Pacific and says New Zealand will "suffer" if nations "look more inwardly".
Jacinda Ardern made the comments in Melbourne on Friday after her bilateral meeting with Australian Prime Minister Scott Morrison.
Ardern said there "has been a view in the past few years" between Australia and New Zealand that there "hasn't been the same level of attention from the United States within our region".
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"That's something that both New Zealand and Australia have been raising publicly, but also in conversation around some of the issues within our region that we do think require attention."
The Prime Minister said in response to what's been a "growing insecurity" amongst populations, "we have seen some political movements look to blame international institutions, the free trade agenda, as contributing to that".
"I really reject that," Ardern said. "Between New Zealand and Australia, there's an opportunity for the both of us to continue to support rules-based trading regimes.
"It is ultimately us as a small trading nation that will suffer if we see more countries look more inwardly off the back of some of those heavily nationalist agendas."
The Prime Minister's comments followed a speech she delivered titled 'Why Good Government Matters' on Thursday evening at an Australia New Zealand School of Government event.
"Nationalist sentiment that closes off the possibility of countries working together is surging. Authoritarian movements and regimes are on the rise," Ardern said, not naming any regime in particular.
"Norms that we in New Zealand and Australia take for granted - the rule of law, the peaceful transfer of power, and freedom of expression - are being challenged in new and more explicit ways."
Ardern said Australia and New Zealand could be "examples to the world" of what it looks like to prioritise international rules and norms "that work for all countries".
The push for free trade
The Prime Minister's comments came just after Foreign Minister Winston Peters stopped off in Washington, DC this week, where he pitched a free trade agreement to US Vice President Mike Pence.
He also said while the US-NZ relationship had only grown stronger, the US' "limited engagement in trade agreements in the Indo-Pacific is of real concern to New Zealand".
US President Donald Trump was elected in 2016 on the back of a campaign that focused on cutting trade ties, including pulling out of the Trans-Pacific Partnership Agreement (TPPA) which New Zealand signed up to.
An updated version of it without the US - the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) - was signed by the New Zealand Government in March last year.
The agreement gives New Zealand better market access to the signatories, including Japan, Canada, Mexico and Peru who New Zealand didn't have existing free trade agreements with.
The Green Party raised concerns about the deal over a clause that gives foreign corporates the right to sue the Government to protect their profits.
Five countries signed deals with New Zealand promising not to sue. Canada and Chile didn't make any promises, except to use the investor-state dispute settlement (ISDS) clauses "responsibly".
The Government's explainer on the ISDS clause says it's "narrower" than the original agreement, and has "strong safeguards to protect the Government's right to regulate in the public interest".