Both Premiership clubs are keen on the striker, who is on-loan at Elland Road from Olympique Marseille.
But any deal may depend on Sakho shaking off a serious knee injury, which was suffered on Tuesday night in a collision with Liverpool goalkeeper Patrice Luzi in a reserves game.
It is likely that the Senegal international, who is coming towards the end of a season-long loan deal from the French club Marseilles, will miss the rest of the season, potentially affecting his hopes of a summer transfer to another club.