The United States will not join an international bid to stamp out violent extremism online.

The United States will not join an international bid to stamp out violent extremism online, the White House said Wednesday, while stressing that Washington backs the initiative's aims.

"While the United States is not currently in a position to join the endorsement, we continue to support the overall goals reflected" in the so-called "Christchurch Call," the White House said.

The initiative is named after the New Zealand city where a far-right gunman massacred 51 people at two mosques in March while broadcasting his rampage live on Facebook. It has been spearheaded by New Zealand Prime Minister Jacinda Ardern and France's President Emmanuel Macron.

The White House said in a statement that the private sector should regulate its content, but also stressed the need to protect free speech.

"We continue to be proactive in our efforts to counter terrorist content online while also continuing to respect freedom of expression and freedom of the press," it said.

"We encourage technology companies to enforce their terms of service and community standards that forbid the use of their platforms for terrorist purposes," it said.

"Further, we maintain that the best tool to defeat terrorist speech is productive speech and thus we emphasize the importance of promoting credible, alternative narratives as the primary means by which we can defeat terrorist messaging."