The federal appeals court announced on Friday that the law – which requires Tiktok to be sold to an American owner by January 19 at the latest or be banned – will not be postponed.
The law was adopted in April this year, motivated by the fact that the USA views Tiktok as a national security risk due to its China-based parent company Bytedance. Tiktok has denied such claims.
In the application submitted last week, Tiktok and Bytedance requested that the enforcement of the law be postponed so that the US Supreme Court would have time to review the case, and so that the incoming Trump administration could "determine its stance" on the matter.
The two companies are expected to appeal to the Supreme Court, but it is unclear whether the court will consider the case.
Donald Trump will take office as the new President of the USA the day after the law comes into effect.