Within hours of joining TikTok, Republican presidential candidate Donald Trump had attracted over 1.3 million followers on the short video social media platform that he tried to ban as president on national security grounds.

The decision to join the platform on Saturday could help the former president reach younger voters in his third bid for the White House. He is in a close race with Democratic incumbent Joe Biden ahead of the Nov. 5 presidential election.

Biden's election campaign is already on TikTok, although Biden has signed a bill that would ban the app, which is used by 170 million Americans, if its Chinese owner ByteDance fails to divest it.

Trump posted a launch video on his account, which has the address @realdonaldtrump, on Saturday night. The video showed Trump greeting fans at an Ultimate Fighting Championship fight in Newark, New Jersey.

Trump campaign spokesperson Steven Cheung said it will leave "no front undefended and this represents the continued outreach to a younger audience consuming pro-Trump and anti-Biden content."

ByteDance is challenging in courts the law that requires it to sell TikTok by next January or face a ban. The White House says it wants to see Chinese-based ownership ended on national security grounds.

TikTok has argued it will not share U.S. user data with the Chinese government and that it has taken substantial measures to protect the privacy of its users.

Trump's attempt to ban TikTok in 2020 when he was president was blocked by the courts. He said in March that the platform was a national security threat but also that a ban on it would hurt some young people and only strengthen Meta Platforms' Facebook, which he has strongly criticized.

Trump already has an active social media presence with more than 87 million followers on X and over 7 million followers on his own platform, Truth Social, where he posts almost daily.

A U.S. appeals court last week set a fast-track schedule to consider the legal challenges to the new law.

The U.S. Court of Appeals for the District of Columbia ordered the case set for oral arguments in September after TikTok, ByteDance and a group of TikTok content creators joined with the Justice Department earlier this month in asking the court for a quick schedule.

  - Reuters