Rangers defender Steven Whittaker has rejected a ''substantially improved'' new contract amid continued interest from Turkish club Bursaspor, according to his agent.
Whittaker is in the final year of his contract at Ibrox, with Rangers attempting to fend off interest from Bursaspor who have reportedly made a fourth offer for the versatile defender.
New Rangers boss Ally McCoist is determined to keep hold of a player he believes is integral to the squad, however, the player's agent Ken Anderson has warned he could make a January move after turning down a new deal.
With the threat of Whittaker leaving on a free transfer, Anderson has also called on Rangers to consider an offer from Bursaspor worth €750,000 (£664,424).
''He'll see out the final year of his contract and we'll talk to other teams in January if Rangers keep rejecting offers,'' Whittaker's agent was reported as saying on the BBC. ''It's up to Rangers if they want to miss out on a transfer fee.''
Last week McCoist admitted the club had received a third offer for Whittaker but denied the player was for sale.
''I can confirm we had an offer from Bursaspor,'' he said. ''I took a phone call from director Andrew Dickson to tell me about it. He didn't even tell me the figures involved because I told him that I wasn't interested in selling Steven.
''I have made it clear that Steven is one of the players I see as part of my long-term plans for the club. That is why we have opened talks with his representatives to extend his current contract.''
Anderson hinted that Whittaker did not feel that the new contract offer reflected his worth to the club, however, adding: ''They say they consider him to be one of their four main players.''
McCoist has so far been frustrated in his initial moves to build upon the squad ahead of his debut season in charge after Israel international Tomer Hemed turned down an offer at the weekend to join Real Mallorca.