Fallout from the March 15 Christchurch terror attack has dominated Jacinda Ardern's United Nations General Assembly speech.

Her speech was in contrast to US President Donald Trump, who used his speech to promote nationalism, telling delegates the "free world must embrace its national foundations".

Ardern took a different approach, saying the world is becoming more interdependent, and that experiences in recent years "should lead us to all question whether any of us ever truly operate in isolation" anymore.

"The world has changed," The Prime Minister said as she delivered her speech to the United Nations General Assembly in New York.

"There are things that we in New Zealand are well known for. Green rolling hills, perfect you might say for hobbits to hide and for plenty of sheep to roam," Ardern said.

"We're known for manaakitanga, or the pride we take in caring for our guests, so much so that it even extends to our most entrenched sporting rivals.

"And now we are known for something else."

Ardern spoke of the March 15 Christchurch terror attack, describing it as the "most horrific attack on a place of worship, taking the lives of 51 innocent people, and devastating our Muslim community".

She said while the attack challenged New Zealanders' sense of "who we are as a country", "We can choose how it defines us".

The Prime Minister praised the people who "lined up outside of mosques with flowers, the young people who gathered spontaneously in parks and open spaces, in a show of solidarity" with the Muslim community.

Ardern pointed out that within 10 days of the attack, the Government "made a decision to change our guns laws and banned military style semi-automatic weapons and assault rifles in New Zealand".

The Prime Minister said changes will "help to make us safer".

"Feeling safe means the absence of fear; living free from racism, bullying, and discrimination. Feeling loved, included and able to be exactly who you are," she said.

"And to feel truly safe, those conditions need to be universal; no matter who you are, no matter where you come from, no matter where you live."

The rest of the Prime Minister's speech focused on the Christchurch Call, a response to the March 15 shootings.

She described it as "bringing together companies, countries and civil society, and committing to a range of actions to reduce the harm this content can cause".

"The alleged terrorist used social media as a weapon," Ardern told delegates.

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"The attack demonstrated how the internet, a global commons with extraordinary power to do good can be perverted and used as a tool for terrorists."

She reflected on how in the first 24 hours after the attack, Facebook took down 1.5 million copies of the livestream video, and how YouTube saw a copy of the livestream uploaded as fast as once every second.

Her comments followed the announcement this week that 31 new countries and two organisations had joined the call, bringing the total to 48 countries and three international organisations.

"Neither New Zealand nor any other country could make these changes on their own. The tech companies couldn't either," Ardern said.

"We are succeeding because we are working together, and for that unprecedented and powerful act of unity New Zealand says thank you."

The Prime Minister also touched on New Zealand's role in responding to climate change.

"There is perhaps no better example of our absolute interdependence than climate change," she told delegates.

"Places like Tuvalu, with a population of just over 11,000 people, barely contributes to global emissions but is paying the price for our collective inaction.

"Atolls so low lying that in weather events the water on either side of it can flow together and join at the narrowest points. Engulfed by the sea."

Ardern said expectations on politicians are "high".

"Meeting those expectations will require us to use every policy lever available - and, just like the Christchurch Call to Action, we need to work with partners inside and outside government to make change."

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She pointed out New Zealand's role in reducing agriculture emissions, which makes up nearly half of our greenhouse gas emissions.

"We can produce the ideas and technology the world needs for everyone to farm and grow in the most sustainable way possible. New Zealand is determined to do good, and be good for the world."

She said this week New Zealand alongside a group of like-minded countries, will announce the launch of a new initiative that "applies trade levers to climate related goods, services and technologies".

The Prime Minister wrapped up her speech by describing the world today as "inherently different" but having "more that we share".

"We may feel afraid, but as leaders we have the keys to create a sense of security, and a sense of hope. We just need to choose."