WASHINGTON, Sept 24 (Reuters) - A U.S. judge said Thursday the Trump administration must either delay a ban on U.S. app stores offering TikTok for download or file legal papers defending the decision by Friday.

The U.S. Commerce Department order banning Apple Inc and Alphabet Inc's Google app stores from offering TikTok app downloads is set to take effect late Sunday. U.S. District Judge Carl Nichols said the government must file a response to a request by TikTok for a preliminary injunction or delay the order by 2:30 p.m. EDT Friday. (Reporting by David Shepardson; editing by Diane Craft)