The Germany international is approaching the end of the deal he signed following a move from Bundesliga outfit Bayer Leverkusen in the summer of 2014.
Asked for the latest on negotiations, Klopp told reporters: "Where the situation is at, at the moment: open.
"That's what we [have] said before, nothing is decided, it's open. We are in talks with him and it's all good so far, apart from him signing a contract for us, that's all.
"No problem with that."