Spurs want to make signings to back Antonio Conte during this month’s transfer window, but have missed out on Adama Traore, who is set to join Barcelona.
The Premier League side are trying to land Diaz from FC Porto, but have had one bid rejected and the Portuguese giants will not let him go for less than his release clause.
Liverpool made initial enquires about Diaz ahead of the January transfer window opening.
And the Reds did not receive good signs from Porto that he would be available this month.
Tottenham look likely to have to trigger his €80m release clause if they want to take him to north London before the window closes.
Porto are currently battling for the Portuguese league title and sit top of the table with a six-point lead over second placed Sporting Lisbon.
Diaz has netted 14 times in just 18 league appearances for Porto this season, despite only operating as a winger.
