WASHINGTON — 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, 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 — which was passed with overwhelming bipartisan support — beginning Sunday, his final full day in office.

“TikTok should remain available to Americans, but simply under American ownership or other ownership that addresses the national security concerns identified by Congress in developing this law,” White House press secretary Karine Jean-Pierre said in a statement, noting that actions to implement the law will fall to the new administration.

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.

TikTok CEO Shou Zi Chew, who is expected to attend Trump’s inauguration, used the app to thank the incoming president for “his commitment to work with us to keep TikTok available.”

It’s unclear what options are open to Trump, a Republican, 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.

The decision explores the intersection of the First Amendment and national security concerns in the fast-changing realm of social media, and the justices acknowledged in their opinion that the new terrain has been difficult to navigate given they know relatively little about it.

“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.”

Some digital rights groups slammed the court’s ruling shortly after it was released.

“Today’s unprecedented decision upholding the TikTok ban harms the free expression of hundreds of millions of TikTok users in this country and around the world,” said Kate Ruane, a director at the Washington-based Center for Democracy & Technology, which has supported TikTok’s challenge to the federal law.

Content creators who opposed the law also worried about the effect on their business if TikTok shuts down. “I’m very, very concerned about what’s going to happen over the next couple weeks,” said Desiree Hill, owner of Crown’s Corner mechanic shop in Conyers, Georgia. “And very scared about the decrease that I’m going to have in reaching customers and worried I’m going to potentially lose my business in the next six months.”