Aberdeen expect midfielder Kari Arnason to leave in the summer after he rejected the club's offer of a new contract.
The 29-year-old, who moved to Pittodrie from Plymouth Argyle last July, has scored three goals for the Dons.
"We made Kari an exceptionally good offer. However, the player believes he can earn a better deal elsewhere," said a club spokesperson.
Arnason scored in the 1-1 draw with Rangers last weekend.
And the Icelandic international has been in impressive form for the Dons this season.
Aberdeen said they were determined to retain Arnason until the summer, adding: "He is crucial to our plans for the remainder of the current campaign, both in terms of climbing up the SPL table and enjoying a fruitful run in the Scottish Cup."
The midfielder's lawyer David Winnie, who is a former Dons player, told BBC Sport: "We are very disappointed we have not been able to reach an agreement."