"It'll either be closed up or they'll sell it," Trump told reporters before leaving for Michigan. "There will be no extension of the TikTok deadline."
TikTok did not immediately respond to a request for comment.
ByteDance has been looking to pick a buyer so it can finalize a deal by mid-September and comply with Trump's order to divest TikTok's assets.
TikTok is best known for videos of people dancing, which go viral among teenagers. But U.S. officials have expressed concern that information on those who use the platform could be passed to Beijing. TikTok has said it would not comply with any request to share user data with the Chinese authorities.