WASHINGTON/NEW YORK (Reuters) -TikTok plans to shut U.S. operations of its social media app used by 170 million Americans on Sunday, when a federal ban is set to take effect, barring a last-minute reprieve, people familiar with the matter said on Wednesday.

The Washington Post reported President-elect Donald Trump, whose term begins a day after a ban would start, is considering issuing an executive order to suspend enforcement of a shutdown for 60 to 90 days. The report did not say how Trump could legally do so.

The law signed in April mandates a ban on new TikTok downloads on Apple or Google app stores if Chinese parent ByteDance fails to divest the site.

Users who have downloaded TikTok would theoretically still be able to use the app, except that the law also bars U.S. companies starting Sunday from providing services to enable the distribution, maintenance, or updating of it.

The Trump transition team did not have an immediate comment. Trump has said he should have time after taking office to pursue a "political resolution" of the issue.

"TikTok itself is a fantastic platform," Trump's incoming national security adviser Mike Waltz told Fox News on Wednesday. "We're going to find a way to preserve it but protect people's data."

The New York Times separately reported that Tiktok CEO has been extended an invitation to attend the President-elect's inaugration and sit in "a position of honor".

A White House official told Reuters Wednesday President Joe Biden has no plans to intervene to block a ban in his final days in office if the Supreme Court fails to act and added Biden is legally unable to intervene absent a credible plan from ByteDance to divest TikTok.

However, a NBC report later said the Biden administration has been weighing options to keep the social media platform avaliable to users beyond Sunday, in a bid to defer the decision to Donald Trump, who will be inaugurated on Monday.

"Americans shouldn't expect to see TikTok suddenly banned on Sunday," an administration official told the broadcast network.

U.S. Senator Ed Markey on Wednesday sought unanimous consent to extend the deadline for ByteDance to divest TikTok by 270 days but Republican Senator Tom Cotton blocked the proposal.

If it is banned, TikTok plans that users attempting to open the app will see a pop-up message directing them to a website with information about the ban, the people said, requesting anonymity as the matter is not public.

"We go dark. Essentially, the platform shuts down," TikTok lawyer Noel Francisco told the Supreme Court last week.

The company also plans to give users an option to download all their data so that they can take a record of their personal information, the sources said.

Users took to social media platform X to express their disappointment with a potential ban on the app, in the run up to Sunday when the ban takes effect. They also expressed their happiness at reports on Trump considering ways to avert the ban.

The U.S. Supreme Court is currently deciding whether to uphold the law and allow TikTok to be banned on Sunday, overturn the law, or pause the law to give the court more time to make a decision.

Shutting down TikTok in the U.S. could make it unavailable for users in many other countries, the company said in a court filing last month, because hundreds of service providers in the U.S. help make the platform available to TikTok users around the world - and could no longer do so starting Sunday.

TikTok said in the court filing an order was needed to "avoid interruption of services for tens of millions of TikTok users outside the United States."

TikTok had said that the prohibitions would eventually make the app unusable, noting in the filing that "data centers would almost certainly conclude that they can no longer store" TikTok code, content, or data.

The sources said the shutdown aims to protect TikTok service providers from legal liability and make it easier to resume operations if President-elect Donald Trump opted to roll back any ban.

Shutting down such services does not require longer planning, one of the sources said, noting that most operations have been continuing as usual as of this week. If the ban gets reversed later, TikTok would be able to restore service for U.S. users in a relatively short time, sources said. 

TikTok and its Chinese parent, ByteDance, did not immediately respond to Reuters' requests for comment.

U.S. tech publication The Information first reported the news late on Tuesday.

Privately held ByteDance is about 60% owned by institutional investors such as BlackRock and General Atlantic, while its founders and employees own 20% each. It has more than 7,000 employees in the United States.

President Joe Biden last April signed a law requiring ByteDance to sell its U.S. assets by Jan. 19, or face a nationwide ban. Last week, the Supreme Court seemed inclined to uphold the law, despite calls from Trump and lawmakers to extend the deadline.

TikTok and ByteDance have sought, at the very least, a delay in the implementation of the law, which they say violates the U.S. Constitution's First Amendment protection against government abridgment of free speech.

TikTok said in the court filing last month it estimated one-third of its 170 million American users would stop accessing the platform if the ban lasted a month.