The Daily Express says the pair are set for a £30million January transfer window battle over Bailey.
The 20-year-old, born in Jamaica, has set the Bundisliga alight this season with eight goals in 16 games for Leverkusen after joining them from Genk in the summer in a £12.4m deal.
Chelsea have been tracking Bailey for some time and were close to making a move for the youngster last season, but have reportedly recently had a £22m offer rejected by the German club.
Bailey made a name for himself in his two-year stint at Genk.
The 20-year-old made 77 appearances, scored 15 goals and produced 21 assists.