Wigan chairman Dave Whelan claims his club have been granted permission to speak to Brentford boss Uwe Rosler.
Stevan Jovetic's agent insists that the Manchester City striker has settled into life in England, despite exit rumours.
Sky Sports revealed earlier on Tuesday that the Black Cats had made a move for the American forward as they continue to reshape their squad under new manager Paolo Di Canio.
But their opening bid has been knocked back by AZ, who have already banked 8 million euros after allowing Adam Maher to join PSV Eindhoven and are not under pressure to sell.
An AZ spokesman told Dutch press agency ANP: "A first bid was insufficient. We have let them know that. Now we have to wait."
Altidore, who has already had a spell in England with Hull City in 2009, enjoyed the best season of his career last term after scoring 23 league goals for AZ Alkmaar.
Sunderland must now consider whether to return with an improved offer for the 23-year-old, or turn their attention to alternative targets.