Sunderland confirmed they have accepted a transfer bid from Watford for defender Younes Kaboul.
The 30-year-old has told manager David Moyes that he wants to leave the Stadium of Light for personal reasons, the club said in a statement.
The former Tottenham man will now hold talks to agree personal terms with Watford after a reported bid of £4million was accepted.
"Sunderland AFC can confirm that it has accepted a bid from Watford for Younes Kaboul," a statement read.
"Younes had spoken with David Moyes in recent days, expressing his desire to leave the club for personal reasons.
"The club therefore agreed to a request from the player's representative to be allowed to speak to Watford regarding a move.
"An agreement has been reached between the two clubs and the player has been given permission to talk to Watford regarding personal terms."
Speaking to Sunderland's official website, Kaboul said: "This is not an easy situation for me, but the club and the manager have shown an understanding of my personal circumstances and I am grateful for that.
"The Sunderland fans have supported me fantastically well since I came to the club, they gave me my passion back and I sincerely thank them for that. I hope they understand that I have made this incredibly difficult decision for me."
Kaboul impressed during the latter part of last season alongside Lamine Kone, who has been linked with a move to Everton.
Moyes has already signed Papy Djilobodji, Paddy McNair and Donald Love to bolster his defensive options, while a new contract has reportedly been offered to Kone to persuade him to stay.
Sunderland, beaten by Manchester City in their opening Premier League match of 2016-17, host Middlesbrough on Sunday.