The 33-year-old will become a free agent once this season ends.
And Klopp says he wants to protect Lallana for his future move.
The German said: "It is clear Adam will leave the club in the summer, if the summer ever starts.
"I already miss everything about him. In this moment he is still here but we will miss him. He is one of the most influential players on the training quality I have ever had in my life. He is an incredible professional.
"But now we have a difficult situation and I will respect Adam a lot. Everything with Adam is sorted, let me say it like this. He is so fit, he is training, everything is fine, but the future is his future. And if we need his help on the pitch we can get it. He trains 100% but as long as we don't need him, he will just train."
Klopp added: "There were a lot of discussions about players without contracts. With him there was not even a discussion.
"It was clear Adam would extend his contract and he wanted to do that as well, but he will not put any risk on his future or whatever. That is absolutely clear. He is one of the most important players of the time since I am here so I wish him only the best for the future. From my point of view he is already a legend here, so he can become a legend somewhere else from next season."