Black Cats boss Sam Allardyce signed the Senegal international in summer 2014 whilst serving as Hammers manager and is seemingly seeking a reunion at the Stadium of Light.
Indeed, Sky Sports claim Sunderland have already tabled an £11million bid for the 26-year-old, who can operate as an out-and-out striker or a wide forward.
Sakho boasts a decent 19 goals in 49 appearances across all competitions for the Hammers, including an impressive return of ten goals in 23 outings from his debut Premier League campaign.
But the former Metz star struggled with injuries last season and managed just seven strikes in the league, finding himself second-choice to Andy Carroll at the end of the campaign.
West Ham have made no secret of their desire to sign a top-quality frontman this summer, which would see Sakho slide further down the pecking order.