That is likely to be worth more than £15million — with the German club valuing the England ace at around £120m.
So they could agree to waiver or renegotiate that in order to gain an advantage over other clubs pursuing Haaland.
City will be in the market for a new striker this summer as they look to find a long-term replacement for all-time leading scorer Sergio Aguero, 32.
And they are waiting to hear if Haaland, 20, son of former City midfielder, Alf Inge, is going to be available this summer.
The starlet can leave Dortmund in the summer of 2022 for a fixed buyout clause of £65m.
But the German giants know some of his admirers are willing to pay a substantial premium in the next few months to avoid missing out.