Spurs are keen to snap Porro up before the transfer window closes on Tuesday night, but have found Sporting Lisbon to be tough negotiators.
There was talk that a deal was done, but that was wide of the mark, with no green light having been given for Porro to join Tottenham.
Discussions are continuing and it has been claimed they are trending towards a positive outcome for Tottenham.
Spurs are standing by to put Porro through his medical paces within the next 24 hours when an agreement is finalised.
Sporting Lisbon have been unwilling to lose Porro throughout the transfer window as he is considered to be a key player.
He started for Sporting Lisbon in their Portuguese League Cup final loss at the hands of FC Porto on Saturday night.
Porro appeared to be saying goodbye to the Sporting Lisbon fans after the final and the expectation remains that he will join Tottenham.