AZ have confirmed they won't be releasing striker Vincent Janssen until their €20 million valuation is met by potential suitors.
Tottenham have seen three separate bids for the Netherlands international rejected by the Eredivisie club, with the most recent bid of €14m coming through on Thursday evening.
AZ technical director Max Huiberts feels there is a short supply of quality strikers around Europe at the moment, hence their valuation of the league's top scorer, who has also been linked with Bundesliga side Wolfsburg.
"The difference between supply and demand is too great," Huiberts told De Telegraaf.
Janssen scored 32 goals and contributed seven assists in 49 games across all competitions in his debut season in the top-flight of Dutch football.