Bellingham is said to have been a target for Manchester United since January and the club have since been on the charm offensive in a bid to secure his signature.
At just 16, Bellingham has become a key figure for the Blues - playing in 32 out of 37 Championship games this season.
He's scored four goals and provided three assists in England's second-tier so far this season and his impressive form continues to attract interest.
But, according to Sport BILD, it's Dortmund who are favourites to land the England under-18 star.
It's understood that Bellingham is ready to reject the advances of Man United, which included a high-level access tour around their Carrington training complex.
The Red Devils were even reported to have sent Sir Alex Ferguson to greet the player and his family in an attempt to persuade them.
Dortmund have a ready-made example of their ability to develop rising British talent in Jadon Sancho, who is breaking Bundesliga records almost every week.
United were rumoured to have submitted a £12.5m bid for Bellingham in January, but it was swiftly rejected by Birmingham.
The Midlands side were thought to be holding out for their valuation of £30m which has reportedly been met by the aforementioned interested parties.
The fee is reported to involve an initial payment of £15m before doubling thanks to various add-ons and bonuses.
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