WASHINGTON, Dec 16 (Reuters) - TikTok made a last-ditch

effort on Monday to continue operating in the United States,

asking the Supreme Court to temporarily block a law intended to

force ByteDance, its China-based parent company, to divest the

short-video app by Jan. 19 or face a ban.

TikTok and ByteDance filed an emergency request to the

justices for an injunction to halt the looming ban on the social

media app used by about 170 million Americans while they appeal

a lower court's ruling that upheld the law.

Congress passed the law in April amid national security

concerns. The Justice Department has said that as a Chinese

company, TikTok poses "a national-security threat of immense

depth and scale" because of its access to vast amounts of data

on American users, from locations to private messages, and its

ability to secretly manipulate content that Americans view on

the app.

The U.S. Court of Appeals for the District of Columbia

Circuit in Washington on Dec. 6 rejected arguments by the

companies and some TikTok users that the law violates their free

speech rights under the U.S. Constitution's First Amendment.

Free speech advocates, including the American Civil Liberties

Union, criticized the D.C. Circuit's ruling.

The D.C. Circuit on Dec. 13 denied an emergency request by

TikTok and ByteDance to temporarily halt the law.

Without an injunction, the ban on TikTok would make the

company far less valuable to ByteDance and its investors, and

hurt businesses that depend on TikTok to drive their sales.

Calling itself one of the "most important speech platforms"

used in the United States, TikTok has said in legal filings that

there is no imminent threat to national security and that

delaying enforcement of the law would allow the Supreme Court to

consider the legality of the ban and the incoming administration

of President-elect Donald Trump to evaluate the law as well.

Trump, who unsuccessfully tried to ban TikTok during his

first term in 2020, has reversed his stance and promised during

the presidential race this year that he would try to save

TikTok. Trump takes office on Jan. 20, the day after the TikTok

deadline under the law.

In its decision, the D.C. Circuit wrote, "The First

Amendment exists to protect free speech in the United States.

Here the government acted solely to protect that freedom from a

foreign adversary nation and to limit that adversary's ability

to gather data on people in the United States."

TikTok has denied that it has or ever would share U.S. user

data, accusing American lawmakers in the lawsuit of advancing

speculative concerns, and has characterized the ban as a

"radical departure from this country's tradition of championing

an open Internet."

TikTok said that being shuttered even temporarily would

destroy its user base, its ability to attract advertisers and to

recruit and retain content creators and employee talent.

The D.C. Circuit's decision came at a time of growing trade

tensions between the world's two biggest economies after

President Joe Biden's administration placed new restrictions on

the Chinese chip industry and China responded with a ban on

exports of gallium, germanium and antimony to the United States.

The U.S. law would bar providing certain services to TikTok

and other foreign adversary-controlled apps including offering

it through app stores such as Apple ( AAPL ) and Alphabet's

Google, effectively preventing its continued U.S. use

unless ByteDance divests TikTok by the deadline.

An unimpeded ban could open the door to a future crackdown

on other foreign-owned apps. In 2020, Trump tried to ban WeChat,

owned by Chinese company Tencent, but was blocked by the courts.