The Dane and his representatives have been in discussions with the Blues hierarchy for a number of months without extending his terms past the end of this season.
Christensen has subsequently spent time on the substitutes' bench, and Tuchel has acknowledged that he is growing frustrated with the lack of progress behind the scenes.
Tuchel is quoted by The Guardian as saying: "My understanding was that it was a matter of a very short period before we had good news. As I understood it, the club wants the same, the player wants the same, the coach wants the same: to stay.
"And that's why for me it was a zero-problem situation, but we are waiting a long time now for confirmation and it's on Andreas to act. How he acts on the pitch, he needs to act now off the pitch and walk the talk because he tells us that he loves Chelsea.
"He tells us that he wants to stay. He is a big part of a big club and I think he is a perfect fit and I think his career here is by far not finished, but, like I said, it's on him. We want the commitment and hopefully we get it."
Christensen has not been given any minutes by Tuchel since the 1-1 draw against Burnley on November 6. body check tags ::