Portuguese newspaper Diário de Notícas journalist Gonçalo Lopes claims Spurs boss Andre Villas-Boas wants two new additions in the January transfer window - with United target Coentrao top of his shopping list.
The Tottenham manager was extremely active in the summer window, putting the £85m received for Gareth Bale to good use.
Spurs bought in Erik Lamela, Etienne Capoue, Paulinho, Roberto Soldado, Nacer Chadli and Christian Eriksen among others over the off-season.
But Lopes claims they will resume spending at the first opportunity in January.
Manchester United failed in a deadline day loan bid for Real Madrid full-back Coentrao, who has fallen behind Marcelo in the pecking order at the Bernabeu.
David Moyes is expected to return in January for the left-back, as he looks to provide competition for Patrice Evra at Old Trafford.
But Spurs are short of cover in the position as well, following Benoit Assou-Ekotto's move to Queens Park Rangers.
Danny Rose is the club's only first-team left-back at the moment, and Villas-Boas has been tipped to move for the former-Benfica star at the earliest opportunity.