TikTok went offline in the United States on Sunday, leaving millions of disappointed users unable to access the popular app, while President-elect Donald Trump pledged to pursue a solution.

Hours before a law banning the Chinese-owned platform in the name of national security came into effect, TikTok was removed from app stores and told users attempting to log on that under the new legislation "you can't use TikTok for now."

It said "we are fortunate that President Trump has indicated that he will work with us on a solution to reinstate TikTok once he takes office. Please stay tuned!"

Trump, who had previously backed a ban and during his first term in office made moves towards one, posted "Save TikTok!" on his own Truth Social platform early Sunday.

The blackout followed a US Supreme Court decision on Friday to uphold the legislation banning the video-sharing platform, unless Chinese owner ByteDance reached a deal to sell it to non-Chinese buyers by Sunday.

From teenage dancers to grandmothers sharing cooking tips, TikTok has won hearts worldwide for its ability to turn everyday users into global sensations through viral videos.

The app has also gained an unexpected supporter in President-elect Donald Trump. Since signing an executive order in 2020 to pressure ByteDance into selling TikTok, Trump has praised the platform for helping him connect with younger voters.

Speaking with NBC News on Saturday, Trump revealed that after discussions with Chinese President Xi Jinping, he is considering granting a 90-day reprieve once he returns to the Oval Office on Monday.

The law permits a 90-day delay if the White House can demonstrate progress toward a viable deal, but ByteDance has firmly rejected any sale.

The outgoing administration of President Joe Biden has stated that it will defer the issue to President-elect Donald Trump and will not enforce the ban.

However, it remains uncertain how the incoming president could lift the ban without ByteDance agreeing to a sale.

"Congress wrote this law to be virtually president-proof," warned Adam Kovacevich, chief executive of industry trade group Chamber of Progress.

Besides removing TikTok from app stores, the law requires Apple and Google to block new downloads, with the companies liable for penalties of up to $5,000 per user if the app is accessed.

Oracle, which hosts TikTok's servers, would also be legally obligated to enforce the ban.

Other social media platforms such as X were flooded with memes and comments mourning the move early Sunday -- though some posts were more cynical, with many pointing to Trump's own previous efforts to ban TikTok.

"Nothing is more American than banning TikTok before AR-15s," posted X user David Leavitt, referring to an automatic weapon often used in US mass shootings.

In Europe, TikTok's suspension drew praise from the foreign minister of Estonia -- among the countries most resilient to disinformation, according to the European Media Literacy Index.

"Banning TikTok must be considered in Europe as well," Margus Tsahkna said on X, adding that the US banned app has been used to spread disinformation and manipulate elections, and is known to pose a national security risk.

The ban even became a hot topic at the Australian Open tennis in Melbourne, where American player Coco Gauff scrawled "RIP TikTok USA" on a courtside camera.

"I could not access it after my match," Gauff said after winning her fourth-round match.

"I love TikTok, it's like an escape... hopefully it comes back," the world number three told reporters.

Offers for TikTok

A last-minute proposal made Saturday by the highly valued start-up Perplexity AI offered a merger with the US subsidiary of TikTok, a source with knowledge of the deal told AFP.

The proposal did not include a price but the source estimated it would cost at least $50 billion.

Frank McCourt, the former Los Angeles Dodgers owner, has also made an offer to purchase TikTok's US activity.

Meanwhile, thousands of worried TikTok users turned to Xiaohongshu ("Little Red Book"), a Chinese social media network similar to Instagram, ahead of the suspension.

Nicknamed "Red Note" by its American users, it was the most downloaded app on the US Apple Store last week.