Italian club Roma claim Argentine forward Erik Lamela is to join Tottenham for £25.7m (30m euros).
The deal for Lamela, 21, also includes up to £4.2m (5m euros) in bonus payments, taking the club's spending to nearly £85m this summer.
The sale could finally enable Gareth Bale's move to Real Madrid to go ahead for a world record fee of £86m.
Spurs are also working on a deal to sign Danish midfielder Christian Eriksen, 21, from Dutch side Ajax.
There is no agreement in place yet and the player would still need to undergo a medical and agree terms.
But Ajax have confirmed that they have given Tottenham permission to talk to the highly rated international.
Ajax boss Frank de Boer told BBC Sport: "There is a snowball effect happening with the Gareth Bale transfer.
"For us, Christian is a key player, so if he leaves before 2 September it is a big setback for the team.
"But there is not a lot we can do. We cannot stop him leaving. He knows how we think about it - he has only one year of his contract left so he has to leave now or sign for another year more with us.
"It is his choice. When the clubs have agreed the transfer, it is for him [to decide] whether he is going to do it or not."
Tottenham's former Ajax defender Jan Vertonghen, who moved to White Hart Lane from the Dutch club for £12m last summer, is a close friend of Eriksen and could be a factor in whether he moves to the London club or not.
Tottenham have already signed Roberto Soldado (£26m), Paulinho (£17m), Etienne Capoue (£9m) and Nacer Chadli (£7m).
The London club are just £2m short of spending as much as Manchester City, who are the Premier League's biggest investors during the current transfer window, recruiting four players for nearly £87m.
Lamela's impending arrival at White Hart Lane could mean that Bale finally completes his switch to Real Madrid.
Tottenham were not ready to let the 24-year-old Welshman leave until they had signed a replacement.
They thought they had signed Willian, but the Brazilian chose to join Chelsea in a £30m deal.
Roma, meanwhile, have announced that they have signed Fiorentina forward Adem Ljajic for £9.4m (11m euros).
The Serbian 21-year-old has signed a four-year deal.