Bayer Leverkusen are interested in signing Celtic defender Kristoffer Ajer.
Sky Germany understands the clubs are in talks over a potential deal for the Norway international.
Ajer, who has one year left on his contract, said last week: "It is probably for the best that something should happen this year."
He has been with the club since 2016 and after a loan spell at Kilmarnock in 2016-17, signed a new four-year deal with the Hoops in 2018.
Sky Italy confirmed last week that AC Milan ended their long-standing interest in the Norwegian to pursue Chelsea's Fikayo Tomori.
Rumours also linked the 23-year-old to Norwich and Newcastle.
When asked about his situation, Ajer, who made 47 appearances for the club in 2020-21 and scored two goals, played down the speculation.
Speaking to a Norwegian press conference, Ajer said: "There are of course a lot of rumours, but as of right now there are only rumours
"I have one year left of the contract and that is what I am focused on, but of course, something might possibly happen this summer.
"I will adhere to that and stay loyal to the club, but in order for both me and the club to have the best possible starting point (for negotiations) it is probably for the best that something should happen this year."
On Monday, Ange Postecoglou verbally agreed personal terms with Celtic to become their new manager.