Shunsuke Nakamura's legal representative has warned Celtic that four clubs are chasing the Japan midfielder.
Angelo Massoni is studying Nakamura's contract to determine whether there is an escape clause that will allow him to leave for around £1m.
Massoni said he has spoken with the player's agent and is hoping to meet the club on the issue.
He added: 'We have four of the biggest clubs in world football interested in Nakamura and willing to pay big money. We will recommend these offers to Celtic.
'Obviously, if Celtic want to make a better offer, that is up to the club.'
