WASHINGTON (Reuters) - Donald Trump has urged the U.S. Supreme Court to pause a federal TikTok law that would ban the popular social media app or force its sale, with the Republican U.S. President-elect arguing that he should have time after taking office to pursue a "political resolution" to the issue.

TikTok and its owner ByteDance are fighting to keep the popular app online in the United States after Congress voted in April to ban it unless the app's Chinese parent company sells it by Jan. 19.

They have sought to have the law struck down, and the Supreme Court has agreed to hear the case. But if the court does not rule in ByteDance's favor and no divestment occurs, the app could be effectively banned in the United States on Jan. 19, one day before Trump takes office.

"This case presents an unprecedented, novel, and difficult tension between free-speech rights on one side, and foreign policy and national security concerns on the other," Trump said in a filing on Friday.

"Such a stay would vitally grant President Trump the opportunity to pursue a political resolution that could obviate the Court's need to decide these constitutionally significant questions," the filing added.

Free speech advocates separately told the Supreme Court on Friday that the U.S. law against Chinese-owned TikTok evokes the censorship regimes put in place by the United States' authoritarian enemies.

Trump indicated earlier this week that he favored allowing TikTok to keep operating in the United States for at least a little while, saying he had received billions of views on the social media platform during his presidential campaign.

The U.S. Justice Department has argued that Chinese control of TikTok poses a continuing threat to national security, a position supported by most U.S. lawmakers.

TikTok says the Justice Department has misstated the social media app's ties to China, arguing that its content recommendation engine and user data are stored in the United States on cloud servers operated by Oracle Corp while content moderation decisions that affect U.S. users are made in the United States as well.