Prime Minister Jacinda Ardern says she doesn't understand the United States' position on gun laws.
Ms Ardern and French President Emmanuel Macron are hosting the meeting of world leaders and tech giants to look at how to stop extremism spreading online. The global call for action comes after 51 people died in Christchurch as the result of a terrorist attack that was livestreamed on Facebook.
Heads of state from Canada, the United Kingdom, Ireland, Norway, Jordan, Senegal, Indonesia and the European Union are attending, though US President Donald Trump is absent.
Speaking to US broadcaster CNN this morning, Ms Ardern said there was no question in her mind that New Zealand's gun legislation had to change after the Christchurch attacks.
"We did have permissive gun laws," she said, as weapons used in the 15 March attacks were easily obtained and modified.
"There was no question in my mind that our laws needed to change."
Parliament supported the change, she said as did New Zealanders by and large.
"It speaks to the strength of feeling in the aftermath of that attack.
"After you witness 51 of your New Zealand Muslim community be attacked in that way the only answer was to to do everything we could to prevent it every happening again."
Asked by CNN's Christiane Amanpour about mass shootings in the United States and whether other countries could learn from the actions of New Zealand and Australia, Ms Ardern said it was possible to "draw a line" and ban access to military style semi-automatic weapons and assault rifles.
"Australia experienced a massacre and changed their laws, New Zealand had its experience and changed its laws.
"To be honest with you I do not understand the the United States."
'We've had good ongoing engagement with Facebook'
Ms Ardern said co-operation on ending extremist content online was the least that should be expected from Facebook.
Mark Zuckerberg from Facebook is absent from the meeting but the social media company's vice-president of global affairs, Nick Clegg, is there.
"I've spoken to Mark Zuckerberg directly, twice now, and actually we've had good ongoing engagement with Facebook. Last time I spoke to him a matter of days ago he did give Facebook support to this call to action."
Ms Ardern said governments cannot ignore the way people are being radicalised, and had a role to play in preventing it.
The Prime Minister is holding a series of one-on-one meetings today with British Prime Minister Theresa May, the King of Jordan, Norway's Elna Solberg and Twitter boss Jack Dorsey.
She will have an hour-long lunch with the French President Emmanuel Macron at the Elysee Palace ahead of the Christchurch Call summit. Tomorrow, she will attend the Tech for Good dinner where she'll make a speech before a meeting with Canada's Prime Minister Justin Trudeau.