WASHINGTON (AP) -- The Supreme Court on Friday unanimously upheld the federal law banning TikTok beginning Sunday unless it's sold by its China-based parent company, holding that the risk to national security posed by its ties to China overcomes concerns about limiting speech by the app or its 170 million users in the United States.

A sale does not appear imminent and, although experts have said the app will not disappear from existing users' phones once the law takes effect on Jan. 19, new users won't be able to download it and updates won't be available. That will eventually render the app unworkable, the Justice Department has said in court filings.

The decision came against the backdrop of unusual political agitation by President-elect Donald Trump, who vowed that he could negotiate a solution and the administration of President Joe Biden, which has signaled it won't enforce the law beginning Sunday, his final full day in office.

Trump, mindful of TikTok's popularity, and his own 14.7 million followers on the app, finds himself on the opposite side of the argument from prominent Senate Republicans who fault TikTok's Chinese owner for not finding a buyer before now. Trump said in a Truth Social post shortly before the decision was issued that TikTok was among the topics in his conversation Friday with Chinese leader Xi Jinping.

It's unclear what options are open to Trump once he is sworn in as president on Monday. The law allowed for a 90-day pause in the restrictions on the app if there had been progress toward a sale before it took effect. Solicitor General Elizabeth Prelogar, who defended the law at the Supreme Court for the Democratic Biden administration, told the justices last week that it's uncertain whether the prospect of a sale once the law is in effect could trigger a 90-day respite for TikTok.

"Congress has determined that divestiture is necessary to address its well-supported national security concerns regarding TikTok's data collection practices and relationship with a foreign adversary," the court said in an unsigned opinion, adding that the law "does not violate petitioners' First Amendment rights."

Justices Sonia Sotomayor and Neil Gorsuch filed short separate opinions noting some reservations about the court's decision but going along with the outcome.

"Without doubt, the remedy Congress and the President chose here is dramatic," Gorsuch wrote. Still, he said he was persuaded by the argument that China could get access to "vast troves of personal information about tens of millions of Americans."

At arguments, the justices were told by a lawyer for TikTok and ByteDance Ltd., the Chinese technology company that is its parent, how difficult it would be to consummate a deal, especially since Chinese law restricts the sale of the proprietary algorithm that has made the social media platform wildly successful.

The app allows users to watch hundreds of videos in about half an hour because some are only a few seconds long, according to a lawsuit filed last year by Kentucky complaining that TikTok is designed to be addictive and harms kids' mental health. Similar suits were filed by more than a dozen states. TikTok has called the claims inaccurate.

The dispute over TikTok's ties to China has come to embody the geopolitical competition between Washington and Beijing.

"ByteDance and its Chinese Communist masters had nine months to sell TikTok before the Sunday deadline," Sen. Tom Cotton, R-Ark., wrote on X. "The very fact that Communist China refuses to permit its sale reveals exactly what TikTok is: a communist spy app. The Supreme Court correctly rejected TikTok's lies and propaganda masquerading as legal arguments."

The U.S. has said it's concerned about TikTok collecting vast swaths of user data, including sensitive information on viewing habits, that could fall into the hands of the Chinese government through coercion. Officials have also warned the algorithm that fuels what users see on the app is vulnerable to manipulation by Chinese authorities, who can use it to shape content on the platform in a way that's difficult to detect.

TikTok points out the U.S. has not presented evidence that China has attempted to manipulate content on its U.S. platform or gather American user data through TikTok.

Bipartisan majorities in Congress passed legislation and Biden signed it into law in April. The law was the culmination of a yearslong saga in Washington over TikTok, which the government sees as a national security threat.

TikTok, which sued the government last year over the law, has long denied it could be used as a tool of Beijing. A three-judge panel made up of two Republican appointees and a Democratic appointee unanimously upheld the law in December, prompting TikTok's quick appeal to the Supreme Court.

Without a sale to an approved buyer, the law bars app stores operated by Apple, Google and others from offering TikTok beginning on Sunday. Internet hosting services also will be prohibited from hosting TikTok.

ByteDance has said it won't sell. But some investors have been eyeing it, including Trump's former Treasury Secretary Steven Mnuchin and billionaire businessman Frank McCourt. McCourt's Project Liberty initiative has said it and its unnamed partners have presented a proposal to ByteDance to acquire TikTok's U.S. assets. The consortium, which includes "Shark Tank" host Kevin O'Leary, did not disclose the financial terms of the offer.

Prelogar told the justices last week that having the law take effect "might be just the jolt" ByteDance needs to reconsider its position.

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