Aberdeen have put a new deal on the table but this is believed to fall considerably short of what Calderwood wants.
Dons manager director Duncan Fraser played down the speculation, but admitted that an offer has been made:
"If Jimmy is on the verge of quitting I've not been made aware of it. An offer is on the table and it is now a case of whether the manager will accept it or not."
However, four of the clubs key players, Barry Nicholson, Zander Diamond, Michael Hart and Chris Clark are yet to sign new deals and have been heavily linked with moves down south. The break up of the team who have reached the last 32 of the UEFA Cup may well have prompted the manager to consider his own future.
Asked if he was set to leave Aberdeen, Calderwood said: "Nothing is certain at this moment. My own contract situation is no nearer to be resolved and we are not that far down the road."