The Prime Minister isn't ruling out changing laws that could go as far as blocking Facebook if it's used to share extremist or violent content like the alleged Christchurch gunman's video of the March 15 terror attack.

Jacinda Ardern is in Paris ahead of her Christchurch Call summit - a meeting with technology giant executives and world leaders gathered to try and tackle the problem of social media being used to spread extremist ideologies.

She's co-hosting the summit in Paris this week with French President Emmanuel Macron, where it's expected countries and companies will pledge to regulate social media, in the wake of the Christchurch attack Facebook livestream.

Here's how the pledge is likely to look:

An expectation about removing violent or extremist content - but with no deadlines given for companies to take down the footage.

Finding ways to identify the content - even if it's been edited - is a priority.

Algorithms could change so if people search for white supremacist content, for example, they aren't directed to more of the same - they could be steered to help services instead.

And a global crisis response system - so in the same way our agencies have plans for earthquakes, they'll be able to take immediate action with terrorism online.

The pledge will not be binding, meaning it's up to individual countries to legislate.

"The pledge is more of a blueprint - law changes will follow," Ardern told Newshub. "Yes, there's work for us to do on our own domestic legislation - we haven't determined what that will look like - that work's yet to come."

The Prime Minister wouldn't rule out blocking websites if they fail to remove extremist content, telling Newshub: "Certainly at this stage [we're] learning from what we see internationally."

When asked if she would consider banning Facebook if it didn't comply, Ardern replied: "I'm not going into the different benefits and costs - we've got to come up with a New Zealand solution."

Websites like 8Chan and 4Chan that were used by the alleged gunman and that routinely spread extremism are on notice.

"We need them in our minds when we think about our domestic legislation," Ardern said.

In Germany, social media companies have 24 hours to take down unlawful content or face fines up to NZ$85 million.

In Australia, if violent material isn't taken down quickly companies face fines of up to 10 percent of their annual profit - for Facebook that would be more than $1.5 billion.

The UK's considering going even further, in extreme cases blocking websites - like Facebook - if they don't comply.

Asked if she expects countries to follow through with the Christchurch Call, Ardern told Newshub: "Absolutely. This is an action plan for the future."

But there's a glaring omission from a global call for action, Donald Trump won't be attending and the Prime Minister doesn't even know who - if anyone - from the United States is coming to her Christchurch Call.

"I don't wish to confirm or otherwise on the United States until we know for certain whether there will be representation."

Newshub.