Participants will be asked to commit to pledges to eliminate terrorist and violent extremist content on social media and other online platforms.
The New Zealand leader earned huge worldwide prominence and respect after the attacks by reaching out to Muslim communities at home and vowing a widescale crackdown on extremist content.
Attendees will also include Canadian Prime Minister Justin Trudeau, Irish Premier Leo Varadkar, British Prime Minister Theresa May and Jordan's King Abdullah II, as well as representatives from Microsoft Corp. and Vivendi SA's DailyMotion.
Prominent figures from tech and social networks will also be present, most notably Twitter founder and chief executive Jack Dorsey, who will also have bilateral talks with Ardern.
The Christchurch call meeting is to get underway around 1400 GMT and finish with a press conference by Ardern and Macron at 1600 GMT.
Ardern also said prior to the ban, New Zealand had "pretty permissive gun legislation", and while she thinks guns are necessary in some instances, she felt the laws went too far. But the White House said in a statement it is "not now in a position to join the endorsement", which leaders from countries such as Australia, Canada and the United Kingdom are expected to sign.
Facebook did not specify which offences were eligible for the one-strike policy or how long suspensions would last, but a spokeswoman said it would not have been possible for the shooter to use Live on his account under the new rules.
"It was created to be broadcast on the internet". Therefore, if a user posted content leading to a terrorist website, they'd be banned from livestreaming.
First-time offenders will be suspended from using Live for set periods of time, the company said.
The company says it will spend $7.5 million to partner with three universities to develop tools preventing modified versions of terror videos from being reposted.
Ahead of a summit on online extremism, Ardern was responding to a question asking whether countries can learn from New Zealand.
Mr Breslin said it was a token measure and lacking in detail.