Jacinda Ardern meets UN Secretary-General António Guterres

Prime Minister Jacinda Ardern has held a formal meeting with the United Nations Secretary-General António Guterres against the backdrop of the escalating war in Ukraine.

Ardern is in New York for the UN general assembly where leaders have gathered to grapple with world crises.

She said the meeting with Guterres covered issues including the war in Ukraine, the role of the Indo-Pacific in the Russia-Ukraine conflict, and also challenges facing the Pacific including climate change.

Ardern said expelling the Russian ambassador was "one of the least meaningful" actions New Zealand could make.

"Amongst all of the options for our strong response to Russia's illegal invasion of Ukraine we've always had a range of options on the table, expelling the Russian ambassador has always been one of those options. We like most of our like-minded partners have not exercised that option because that is one of the least meaningful in this situation.

"Sanctions send the strongest message. We as politicians have all been banned from travelling to Russia for our sanctions not because of diplomatic expulsions."

Ardern said her conversation with Guterres discussed how the international community could make it clear it remained united amid the recent escalation of military rhetoric by Russian President Vladimir Putin.

"Our conversation was very much in those more general terms, how do we continue to make sure that we have that international community in its full force across regions, not just in Europe but of course across Asia, the Pacific, Latin America, the Caribbean so that it is very clear that the international community stands united on this clear breach of the international rules and order."

A UN statement released after the meeting said Guterres thanked New Zealand for its "stalwart support to multilateralism".

"The secretary-general and the prime minister exchanged views on global security, including the consequences of the war in Ukraine, as well as challenges facing the Pacific region," the statement said.

Ardern is set to make a speech to the UN General Assembly tomorrow, and she said the content of the speech would surprise no one.

"I hope that I'll capture the sentiment that New Zealanders will want shared here and that is that we have a responsibility as leaders, a duty of care to keep our people safe and to keep not only our own backyards but also the international environment we live in as peaceful as possible."

Ardern called for reform of the UN saying its security council had failed to fulfil its purpose.

"The UN is usually the body by which we operate with our sanctions but even in lieu of that you've still seen the international community act.

"We need reform of the UN. It's simply not good enough that we've had to act bilaterally, we've had to act on our own to make sure that we're seeing those consequences for Russia because of the veto and the failure of the security council."

Expelling Russia from the UN was not the right option as it would mean Russia did not have to face condemnation from the West, Ardern said.

Ardern said her criticism of the UN security council operates was directed towards the members who have moved to protect their national interests by pushing to retain the veto option.

She said it seemed there had been a "hiatus" of international discussion around furthering nuclear non-proliferation but "now more than ever it needs to be at the top of the agenda".

Ardern yesterday met Ukrainian Prime Minister Denys Shmyhal, reaffirming New Zealand's support.

Ardern today reiterated Foreign Affairs Minister Nanaia Mahuta's views that expelling the Russian ambassador had "always been on the table, always been under active consideration".

"I really am firming up the view that in their mind the most important thing we could be doing is first and foremost sanctions and also supporting them as we have in the ongoing fight in Ukraine."

Ardern said Ukraine had never asked New Zealand to expel its Russian ambassador.

She attended President Volodymyr Zelensky's "powerful" address to the general assembly and joined a standing ovation at its conclusion.

Climate change, challenges in the Pacific

She also briefly attended a climate function for Pacific leaders chaired by Fiji Prime Minister Frank Bainimarama and was invited to give an impromptu speech.

"When it comes to the most significant security issue that our region faces, it is by far and away the issue of climate change," Ardern said.

Tonight, New Zealand's delegation would co-host a meeting of Pacific Island leaders alongside Bainimarama, Ardern said.

Some countries worry the focus on Russia's war is displacing other existential crises such as the climate crisis.

The war in Ukraine was "on everyone's minds" particularly due to the escalation in the language used by Russia which in turn signalled an escalation of the conflict in Ukraine, Ardern said.

However, this did not mean other global crises, such as climate change, were not being discussed, she said.

"The majority of my day-to-day has been spent talking with other leaders about the crisis of climate change and the impact on small island nations so from my perspective it's not a matter of one issue dominating, it's a matter [of] multiple crises we're dealing with as an international community."

Ardern has found time for other events on the sidelines: overnight she sat down with Chile President Gabriel Boric for the first time.

Ardern yesterday attended a reception hosted by United States President Joe Biden which was open to all leaders.

She said she also had a brief conversation with Biden while in London for the Queen's funeral.

She earlier told media that Putin's actions were an "extraordinary escalation" of the conflict and called for a "rallying cry from the world".

"What you see in Ukraine is illegal," Ardern said. "It is immoral."

"It is causing a loss of civilian life, and that loss could extend if - as Putin has claimed - he expands the types of weapons used in this war," she said.

Guterres opened leaders' week, warning of a coming "winter of global discontent".

"We cannot go on like this," he said. "We have a duty to act - and yet we are gridlocked in colossal global dysfunction."