Crystal Palace have agreed a £14m fee with Sunderland for Patrick van Aanholt, according to Sky sources.
The Dutch international has handed in a transfer request at the Stadium of Light and will now have a medical in London after being granted permission to open contract talks.
Van Aanholt moved from Chelsea in 2014 for £1.5m but is now set to be reunited with his old manager Sam Allardyce at Selhurst Park.
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Sunderland chief executive Martin Bain said: "If a player openly states, he does not want to play for our club, it is clear that we have a decision to make.
"In this instance and in regard to this particular player, we have done what we feel is right for Sunderland, which will always be our priority."
Van Aanholt will be Allardyce's second signing since he took charge of Palace as Alan Pardew's replacement last month.
Jeffrey Schlupp also moved from Leicester City, meaning this latest deal will take the club's January spending to £27m.
Van Aanholt, a scorer of three goals this season against Middlesbrough, West Brom and Watford, has made 95 appearances for Sunderland.