The 24-year-old winger is in the final year of his contract at Barcelona and so far there is no agreement over a new deal with the club.
The Catalan giants have been trying to convince him to sign on fresh terms, but have not yet succeeded, and want a decision from him in the coming weeks.
Newcastle are reportedly in talks with Dembele to sign him on a free transfer next summer and are prepared to offer him a five-year contract worth €15m per season.
But according to Barcelona-based daily Sport, the Catalan giants are ready to get tough to force the Frenchman into signing a new contract.
It has been claimed that Barcelona will force Dembele to spend the rest of the season in the stands if he does not sign a new deal.
The Catalan giants do not want to lose him on a free transfer and have taken a hardline stance to force the issue.
Barcelona are prepared to banish him from the first-team squad and not let him play a single minute of football if a new contract is not agreed.
As things stand, Dembele will be free to agree on a pre-contract with any of his suitors from January onwards.