Ardern says she is glad the US is on board.
"It's something that we have been working on from the very beginning [having the US involved]....social media platforms are not a place for violent extremists and terrorists. Right from the beginning the United States has been involved, they have been working closely with us, they just haven't signed on."
She would not say whether it was Trump's influence which caused the hold up from the US.
"It's not for me to explain the decision making of the United States," she told The AM Show.
"It's fair to say that certainly this [Biden] administration has said this is a priority for them and they have said that they will participate."