The US is not joining a pledge by 17 countries and major tech companies to stand against online terrorism and extremism in the wake of the deadly mosque attacks in New Zealand, the White House has announced.

The Christchurch Call was unveiled Wednesday in Paris by New Zealand Prime Minister Jacinda Ardern and French President Emmanuel Macron, who were joined by other world leaders, as well as representatives of companies such as Facebook, Google, and Twitter.

In the first 24 hours after the March 15 attack, the gunman's livestreamed video was posted 1.5 million times on Facebook alone, Ardern said earlier this week.

"This was a terrorist attack that was designed to go viral," she said.

The call aims to prevent that from happening again by getting governments and tech companies to work together on solutions. Signatories agreed to enforce existing laws on the dissemination of terrorist content while also considering new tech industry standards and government regulations to keep extreme, violent content like the Christchurch video from once again going viral.

"Social media companies, these platforms, they’re global, so the response needs to be global," Ardern said.