Norwich City are set go back in with a renewed £12 million bid for Kristoffer Ajer.
The newly-promoted Premier League side has already had a number of bids rejected, as have German side Bayer Leverkusen, for the Norwegian international.
The Canaries have made a central defender a priority and Ajer has been a long-term target.
They are ready to make a bid with future add-ons built in.
Ajer, 23, is in the last year of his contract and Celtic will need to sell in this window if they want to maximise their return, having bought the Norwegian international for a bargain six figure fee in 2016 from IK Start.