Millions of TikTok users in the United States can no longer watch videos on the social media platform as a federal ban on the popular app takes effect.

New U.S. law bans use of the platform Already effective Sunday, the day before President-elect Donald Trump’s inauguration. The ban comes after months of legal battles and intense scrutiny of TikTok’s Chinese ownership.

“The United States has enacted a law banning TikTok,” said a message sent to users trying to use the app, which is used by 170 million Americans. “Unfortunately, this means you can’t use TikTok right now.”

Trump said in an interview with NBC News on Saturday that he was considering giving TikTok a 90-day extension so that they can continue to operate. Trump, who has supported a ban on TikTok, said if such an extension happened, it would “most likely” be announced on Monday, the day he is sworn in as president.

TikTok CEO Shou Chew is expected to attend Trump’s inauguration in a prime location.

“We are fortunate that President Trump has said he will work with us on solutions to restore TikTok after taking office,” the app said in a message to US users. “Stay tuned!”

On Friday, the U.S. Supreme Court uphold the law Unless parent company ByteDance divests TikTok’s U.S. operations, the app will be forced to be banned. The ruling marks a significant escalation in efforts to restrict the app, which officials claim poses a national security threat.

In court, the Biden administration has defended the law, citing concerns that TikTok collects vast amounts of U.S. user data that the Chinese government could obtain through coercion.

Officials also warned that the app’s algorithm, which determines what users see, could be manipulated by Chinese authorities to affect the platform in subtle and undetectable ways.

However, the United States has yet to disclose evidence that TikTok shared user data with Chinese authorities or changed its algorithm to serve Chinese interests.

ByteDance denies any wrongdoing and has resisted calls to sell its U.S. operations, leaving the platform in trouble.

U.S. law requires Apple and Google to remove TikTok from their app stores and block new downloads. The companies could face fines of up to $5,000 for each user who has access to the app.

Oracle, which hosts TikTok servers, also has a legal obligation to enforce the ban.

Meanwhile, U.S. rivals such as Instagram Reels and YouTube Shorts will benefit from TikTok’s forced absence.

Another Chinese platform, Xiaohongshu, has gained traction among U.S. users, becoming the most downloaded app on Apple’s U.S. store this week.

Some investors have come up with last-minute solutions to keep TikTok afloat.

Jeff Bezos-backed artificial intelligence startup Perplexity AI has submitted a plan to merge with TikTok’s U.S. operations to create a new entity, which could allow ByteDance to retain partial ownership, according to media reports.

Other bids are still under consideration, including a $20 billion bid from a consortium led by Canadian investor Kevin O’Leary and billionaire Frank McCourt.

Experts warn that even if Trump issues an executive order to delay the ban, he could face legal challenges.

“Congress actually enacted this law to prevent the president’s conduct,” warned Adam Kovacevich, CEO of the Progressive Chamber of Commerce, an industry trade group.