Details at this stage are limited but Ardern said more information will be provided in the coming weeks.
Speaking to media in Auckland, Ardern spoke of creating a "broad alliance" between Governments and tech companies to address the problems.
"We can't, I think, step away from that responsibility. But nor can internet companies step away from theirs as well."
She said to meet the Christchurch Call's goal, Governments and tech companies need to work together.
"That's the sort of collaboration [Governments] have been seeking, and that's what we are responding to."
Ardern said she had spoken to "a range" of tech sector chief executives, including those from Facebook, Twitter, Microsoft and Google.
The response we have received so far has been "really positive".
She has spoken to Zuckerberg personally about the initiative.
The conversation, she said, was "very much around the 15th of March, our experiences and what we hoped to do collaboratively in France when we come together".
She said there were condolences shared when the pair spoke, but Ardern did not want to get into individual details of that conversation.
Across the next two days, Ardern would be meeting tech companies and a "core group of leaders".
Information on who those leaders were will be made available "further down the track," as will more information about the event itself.
But the end of the summit would not mark the end of the issue of extremism online, Ardern told media this afternoon.
"We will be looking over a period of time to try and bring on board, as many countries and companies as we're able."
She pointed out that freedom of speech would not be under attack.
"We're very focused on eradicating those extreme acts of terrorism online".
She said extremism online was a global issue, that required a global response.
