A lawyer for TikTok and Chinese parent company ByteDance sought on Monday to convince a federal appeals court to block a US law that would ban the short video app used by 170 million Americans as soon as January 19, arguing that it violates free speech protections, but faced tough questions from the judges.

A three-judge panel of the US Court of Appeals for the District of Columbia heard two hours of arguments in the lawsuit filed by TikTok and ByteDance in May seeking an injunction to prevent the law from taking effect.

Justice Department lawyer Daniel Tenny pressed the US government's stance that TikTok, under Chinese ownership, poses a national security threat because of its access to vast amounts of personal data on Americans, asserting that China can covertly manipulate information that Americans consume via the popular app.

Andrew Pincus, the lawyer arguing for TikTok and ByteDance, told Judges Sri Srinivasan, Neomi Rao and Douglas Ginsburg that the US government had not demonstrated that TikTok actually poses national security risks. Pincus also argued that the law violates the US Constitution on a number of grounds including running afoul of the First Amendment protections against government abridgment of speech.

The law gives ByteDance until January 19 to sell or divest TikTok's US assets or face a ban in the United States. Driven by worries that China could access data on Americans or spy on them with the app, the US Congress passed the measure with overwhelming support and President Joe Biden signed it into law in April.

The lawsuit claimed that if the statute is upheld, it would show that Congress can circumvent the First Amendment "by invoking national security and ordering the publisher of any individual newspaper or website to sell to avoid being shut down."

TikTok and the Justice Department have asked for a ruling by December 6, which could allow the US Supreme Court to consider any appeal before a ban takes effect.

The White House has said it wants to see Chinese-based ownership ended on national security grounds, but not a ban on TikTok. Trump, who unsuccessfully tried to ban TikTok in 2020, has said if elected in November he would not allow TikTok to be barred. (Reuters)