Days before the start of the Premier League season, Lamine Kone has reportedly asked to leave Sunderland, with Everton believed to be chasing his signature.
The Ivory Coast defender, who is under contract until June 2020, claimed an expected improvement to his deal has not materialised, prompting him to try and force a move.
"At the end of the season I was told by the club that I would be offered a new contract. Following numerous phone conversation and face-to-face meetings, the latest of which took place today with [manager] David Moyes and [chief executive] Martin Bain, no contract has been forthcoming," he was quoted as saying by Sky Sports.
"It is therefore with much regret that I can only assume that I do not figure in David Moyes' future plans.
"With that being the case, it is with much sadness that I have asked the manager and the chief executive to be allowed to leave Sunderland Football Club.
"However until that time, I give my word that I will give my utmost in training and on the field."
Kone reportedly travelled to Goodison Park during the week, intent on finalising a transfer to Everton, who are in need of reinforcement in central defence following the sale of John Stones to Manchester City.
Signed from Lorient in January for an undisclosed fee believed to be close to £6million, the 27-year-old Kone played a crucial part in Sunderland avoiding relegation under Sam Allardyce last season.
Sunderland on Thursday announced the signing of Paddy McNair and Donald Love from Manchester United.