Prime Minister Justin Trudeau is expected to sign an international pledge in Paris Wednesday aimed at getting governments and social media companies working together to curb the spread of violent and extremist content online.

Trudeau is attending the Christchurch Call meeting in Paris. New Zealand Prime Minister Jacinda Ardern, who is co-chairing the meeting with French President Emmanuel Macron, is expected to cite the massacre of 51 Muslim worshippers in two New Zealand mosques in March as she pushes for a sweeping agreement to combat terrorist content disseminated on social media.

In a press release announcing the Paris visit last week, Trudeau voiced his fear that social media platforms increasingly are being weaponized "as tools to incite, publish and broadcast extremist violence and hatred."

He called for "a coordinated global response" to tackle the problem. And while the details of the non-binding pledge up for approval in Paris tomorrow are sketchy at this point, the New York Times reports it will call on social media firms to examine software that directs users to violent content and ask them to share more data with government authorities to find and eliminate violent, extremist material.

People comfort each other outside the Al-Noor mosque on March 22, a week after a pair of attacks on two mosques in Christchurch, New Zealand killed 51 people and injured dozens more. (Edgar Su/Reuters)

The summit came together in the wake of gun attacks on two Christchurch mosques in March that left 51 dead. Video of the attacks was live-streamed for nearly 17 minutes on social media and was subsequently uploaded thousands of times, as social media companies struggled to remove it.

The leaders of the United Kingdom, Ireland, Norway, Indonesia and Senegal, and the president of the European Commission, will also be in Paris, along with high-level officials from Facebook, Twitter, Google and Microsoft. All are expected to endorse the agreement.

The United States, which has been reluctant to regulate the internet due to concerns about limiting freedom of speech, was not invited to attend the Christchurch Call summit and is not expected to sign the pledge.

No right to 'broadcast mass murder'

Ardern has long insisted her push to control the amplification of hate online is not about curbing freedom of expression.

"That right does not include the freedom to broadcast mass murder," she wrote in a recent column.

"This is not about undermining or limiting freedom of speech. It is about these companies and how they operate."

U.K. Prime Minister Theresa May is expected to use her time in Paris to call on governments and social media companies to work together in blocking hateful content.

"The internet is global and online threats have no borders. Companies should be held to consistent international standards, so their customers enjoy the same level of protection wherever they live," May said in a statement.

Trudeau spoke by phone with Microsoft president Brad Smith Monday night ahead of the Paris meeting. According to an account released by the Prime Minister's Office, he spoke about how governments could work with social media platforms to "stop the internet being used as a tool to organize and promote terrorism and violent extremism."

Zuckerberg a no-show

In an op-ed published in the New York Times on Saturday, Ardern called for a "voluntary framework that commits signatories to counter the drivers of terrorism and put in place specific measures to prevent the uploading of terrorist content."

The word "voluntary" is key; the pledge is not expected to include enforcement measures, leaving it up to nations and the social media companies themselves to find ways to restrict the spread of terrorist content online.

While the largest tech companies will be at the table, some of those responsible for running anonymous internet forums known for extreme content — such as 8 Chan and 4 Chan — are not taking part in the summit.

Neither is Facebook CEO Mark Zuckerberg. The social media giant is instead sending Nick Clegg, its vice-president for global affairs and a former deputy prime minister of the U.K.

As part of his visit to Paris, Trudeau also will speak about promoting trust in the online world at VivaTech, an annual technology conference focused on start-ups and innovation.