New Zealand Prime Minister has used a foreign policy speech in Australia to call for reform to the United Nations following Russia's invasion of Ukraine.
Speaking at the Lowy Institute in Sydney, Ms Ardern said the global body needed to be improved so Russia could be further held to account for its military action.
"We must reform the United Nations so that we don't have to rely on individual countries imposing their own autonomous sanctions," she said on Thursday.
"We must also resource the International Criminal Court to undertake full investigations and prosecution of the war crimes and crimes against humanity committed in Ukraine."
New Zealand is set to be a third party in Ukraine's case against Russia in the International Court of Justice following the invasion earlier this year.
Ms Ardern identified the UN's failure to act on the conflict due to Russia's position in the body's Security Council, describing it as a morally bankrupt position.
"Under these circumstances, waiting for our multilateral institutions to act was not an option for New Zealand," she said.
The prime minister said diplomacy needed to be the strongest tool to de-escalate tensions in the region, saying the conflict shouldn't be characterised as a war of the West against Russia.
"We won't succeed, however, if those parties we seek to engage with are increasingly isolated and the region we inhabit becomes increasingly divided and polarised," she said.
"We must not allow the risk of a self-fulfilling prophecy to become an inevitable outcome for our region."
Ms Ardern is on an Australian visit aimed at strengthening trade and security ties.
Climate change 'must be a foreign policy priority'
Ms Ardern also urged Australia to pull in the same direction as New Zealand as she lobbies for more funding to address climate change in the Pacific.
"Climate change must be a foreign policy priority," she said.
Well-founded concerns over the militarisation of the Pacific should be matched with a focus on the violence of climate change, she said on Thursday.
She referred to Australia as New Zealand's largest trading partner, its only formal ally, its largest market for foreign investment and the place where 40 per cent of foreign arrivals in New Zealand landed in 2019.
"We share our people, our problems and our solutions," she said.
"When we look to our principles, co-operation, values and place, we naturally find you within them.
"We won't always agree, and nor should we, but it's true that in the messy world we live, friendship matters."
New Zealand had committed $1.3 billion to climate change, with at least 50 per cent of that spend going to the Pacific, she said.
The Pacific Island Forum (PIF) could play a role establishing climate mitigation projects, where foreign aid could be directed.
Ms Ardern and Prime Minister Anthony Albanese will attend the PIF next week.
"Not every external aid and development donor will have the capability to access our neighbours individually," she said.
"We need to look to the role we can play to bring in that support on the terms the Pacific sets, and the PIF is a great way to do that."
Later on Thursday Ms Ardern will hold talks with Premier Dominic Perrottet at NSW parliament.
On Friday, Ms Ardern will see Mr Albanese after they briefly met shortly after the Australian federal election in May.
The leaders' meeting is expected to cover labour shortages, economic links, regional security, Indigenous cooperation, migration, economic recovery and climate change.
