The Swiss, 28, is currently tied to 2021 and admits he sees a future for himself in England.
Burki said: "As a kid, I was a fan of Manchester United - with Edwin van der Sar in goal.
"This is already a club that triggers something in me. However, to be 100% happy in my career, I do not have to move to England.
"I feel very comfortable in Dortmund."