TikTok says it's 'restoring service'

TikTok said Sunday it's "restoring services" after a ban in the United States initially began to take effect earlier in the day.

"In agreement with our service providers, TikTok is in the process of restoring service. We thank President Trump for providing the necessary clarity and assurance to our service providers that they will face no penalties providing TikTok to over 170 million Americans and allowing over 7 million small businesses to thrive," the company said in a statement. "Its a strong stand for the First Amendment and against arbitrary censorship. We will work with President Trump on a long-term solution that keeps TikTok in the United States."

When users returned to the app Sunday, they were greeted by a message that said, "Welcome back! Thanks for your patience and support. As a result of President Trump's efforts, TikTok is back in the U.S.! You can continue to create, share and discover all the things you love on TikTok."

This comes after TikTok briefly went dark between late Saturday night and early Sunday.

Last spring, Congress passed a measure with overwhelming bipartisan support granting TikTok a 270-day window to cut its ties with China-based parent company ByteDance or face a ban in the U.S. Instead of initiating a sale, however, TikTok pursued a legal challenge on First Amendment grounds that ended in failure at the Supreme Court on Friday.

The unanimous ruling from the nation's highest court found merit in national security concerns regarding potential user data collection or content manipulation that the Chinese government might undertake.

The platform became unavailable for some users Saturday evening, with a pop-up message in the app saying, "Sorry, TikTok isn't available right now."

"A law banning TikTok has been enacted in the U.S. Unfortunately, this means you can't use TikTok for now," the message went on. "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!"

By Sunday morning, App stores run by Apple, Google and Samsung began removing the app.

The Biden administration said earlier this week that it would not enforce the ban on Sunday, leaving implementation of the measure to President-elect Donald Trump, who takes office on Monday. Trump has vowed to reverse the ban.

In a Truth Social post on Sunday morning, Trump said he's "asking companies not to let TikTok stay dark!" He said he would issue an executive order on Monday, his first day in office, "to extend the period of time before the laws prohibitions take effect, so that we can make a deal to protect our national security."

"The order will also confirm that there will be no liability for any company that helped keep TikTok from going dark before my order," he added.

Trump said he wants "the United States to have a 50% ownership position in a joint venture." He said this could be a joint venture between the current owners and new owners.

Earlier Sunday, a Biden administration official accused TikTok of trying to "blame" the situation on the Biden administration, saying "they've had a year to deal with it and we were clear we wouldn't implement it on our final day."

White House officials had stressed for days that if TikTok were to go dark on Sunday, it would not be because of U.S. enforcement -- it would be TikTok's decision, and that the administration is only kicking the issue to Trump because of the timing.

ABC News' Michelle Stoddart and Selina Wang contributed to this report.

The video in the player above is from a previous report.