Christensen has been locked in discussions with the Chelsea hierarchy for some time now over a new deal but despite signs of progress, the two parties are yet to come to an agreement.
Christensen's current contract expires at the end of the season.
Christensen is one of Chelsea’s longest serving players, having joined the club as a teenager in 2012 before making his first team debut in 2014.
The 25-year-old has had to bide his time before becoming a regular at Stamford Bridge, spending two years on loan in the Bundesliga with Borussia Monchengladbach between 2015 and 2017.
The Denmark international has since become an important part of the Chelsea set-up and has made 12 appearances across all competitions this season.
"I have no good news," Tuchel said. "That was my understanding weeks ago that Andreas wants the same as me, that he wants the same as the club, and that’s why for me it was a zero problem situation because everybody wanted the same as far as I understood it.
"We are waiting since a long time now for confirmation. It is 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 and be a big part, because he is a big part of a big club, and I think he is a perfect fit and I think that he is not done yet here.
"His career here is, by far, not finished, [he] can still develop and be big, big player, but like I said, it’s on him, it’s on him. We want the commitment and, hopefully, we get it."
Christensen was part of the Chelsea sides that won the Europa League in 2019 and the UEFA Champions League last season.
