ECHO WANG and DAVID SHEPARDSON THE Biden administration has demanded that TikTok's Chinese owners divest their stakes in the popular video app or face a possible U.S. ban, the company told Reuters. The move is the most dramatic in a series of recent steps by U.S. officials and legislators who have raised fears that TikTok's U.S. user data could be passed on to China's government. ByteDance-owned TikTok has more than 100 million U.S. users. It is also the first time under the administration of Democratic President Joe Biden that a potential ban on TikTok has been threatened. Biden's predecessor, Republican…