The Portuguese club want over £70m for the playmaker, but Spurs are so far only willing to make a bid that involves £50m straight cash and around £10m in conditionals.
Fernandes himself has already indicated his willingness to go to Spurs, who face a race against time to get the deal done.
Mauricio Pochettino is intent on bringing in more signings, after making his frustration at the situation clear.
The Fernandes deal is linked to Christian Eriksen's future, but not completely dependent on it.
With the Dane's contract set to run out next year, and no sign of a new deal being agreed, Spurs would prefer to move him on this summer and build.
Real Madrid's interest has cooled, however, and Eriksen is left with few options other than Manchester United.
His camp have already rebuffed them in the past, but are more open to it now, and are said to be considering the offer.
On the pitch, at least, Fernandes could serve as a direct replacement for Eriksen.
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