Chelsea have rejected a loan with an obligation to buy bid from Dortmund for midfielder Carney Chukwuemeka and have opened talks with Bayern Munich for Christopher Nkunku.
The Blues are believed to be growing frustrated with Dortmund over ongoing talks for Chukwuemeka and will only entertain permanent offers for the midfielder.
Chukwuemeka spent the second half of last season on loan at the German club but also agreed a new contract at Stamford Bridge which included a £40m release clause.
There remains a gap in valuation of nearly £20m but Chelsea are willing to accept less than the agreed clause as long as suitable add-ons and a sell-on clause are included.