Sunderland have failed with an initial bid for AZ Alkmaar striker Jozy Altidore.
It was reported on Tuesday that the Premier League club have made an offer for the 23-year-old American international.
An Alkmaar spokesman told Dutch news agency ANP: "A first bid was insufficient. We have let them know that. Now we have to wait."
Altidore, who joined AZ from Villarreal in 2011, had a loan spell with Hull City during the 2009-10 campaign.