WASHINGTON (Reuters) -Democratic Senator Ed Markey and Republican Senator Rand Paul on Thursday urged President Joe Biden to extend by 90 days a Jan. 19 deadline for China-based ByteDance to sell the U.S. assets of its short-video app TikTok or face a ban.

The Supreme Court said on Wednesday it will consider the legal challenge of TikTok and ByteDance, seeking an injunction to halt the looming ban or sale and will hold arguments on the matter on Jan. 10. "Given the law's uncertain future and its consequences for free expression, we urge you to trigger the 90-day extension before January 19," the senators wrote Biden.

The White House and TikTok did not immediately comment. The challengers are appealing a lower court's ruling that upheld the law. TikTok is used by about 170 million Americans. Congress passed the measure in April and Biden, a Democrat, signed it into law. The Justice Department had 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. TikTok has said it poses no imminent threat to U.S. security.  

TikTok and ByteDance say the law violates free speech protections under the U.S. Constitution's First Amendment. 

Senate Republican leader Mitch McConnell on Wednesday, in a brief filed with the Supreme Court, urged the court to reject any delay, comparing TikTok to a hardened criminal. Other senators like Republican Josh Hawley and Democrat Richard Blumenthal say ByteDance must follow the law.

Republican President-elect Donald Trump, who unsuccessfully tried to ban TikTok during his first term in the White House in 2020, has reversed his stance and promised during the presidential race this year that he would try to save TikTok. Trump said this week he has "a warm spot in my heart for TikTok" and that he would "take a look" at the matter.

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