The report claims that there was a secret meeting between Bayern and LIAN Sports, who represent Sane and Jerome Boateng, in Munich this week.
Sporting director Hasan Salihamidzic was believed to be representing Bayern at the meeting with one of Europe's biggest agents Fali Ramadani.
Sane and his family were reported to be using David Beckham's London based agency to help engineer a move, but it's understood they have since stopped collaborating.
As per the report, the two negotiating parties can only engage in official conversations from April 1st - things are expected to then move quickly.
It's said that Bayern Munich will offer Sane a substantial five-year-deal before agreeing a fee with Manchester City.
The 24-year-old's camp has reportedly already indicated to the Bayern board that he is ready and willing to make the move.
The Spanish heavyweights could make moves of their own for Sane as they look to revamp their squads after both experiencing underwhelming campaigns thus far.
The identities of the two clubs who have reportedly made offers to the 21-capped German international remain unknown.
It's estimated that any club who ends up buying Sane will have to pay approximately €100m (£92m).
Even though his current contract ends in 2021, Sane is seen as one of the biggest talents of his age bracket in the game.
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