Update report from BBC Scotland website:
Dons duo set for Pittodrie exit
Nicholson and Hart are set for the Pittodrie exit
Barry Nicholson and Michael Hart will not sign the new deals Aberdeen have offered them, BBC Scotland understands.
Both players - along with Zander Diamond and Chris Clark - are out of contract at the end of the season and had all been set a Monday deadline.
The Dons have called a Tuesday media conference amid growing speculation concerning the future of manager Jimmy Calderwood as well as that quartet.
The players are free to negotiate with other clubs.
Aberdeen director of football Willie Miller told BBC Sport that the club had made the best offers possible.
He also revealed that Plymouth boss Paul Sturrock had made an enquiry about one of the four but had not tabled an offer.
Calderwood's future has been under scrutiny for some time and the club would only say that talks with the former Dunfermline manager are on-going and reasonably positive.
"Nothing is certain," Calderwood told the P&J. "My own contract situation is no nearer to being resolved and we are not that far down the road.
"The situation is I am waiting for the club to get back to me.
"But it is wrong for people to jump to a conclusion where negotiations with the players and the club, and my own talks about a new contract, are linked."
The club aim to keep Calderwood at the helm and managing director Duncan Fraser said: "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."