The 25-year-old defender is out of contract at the end of the season and Black Cats boss Paolo Di Canio is eager to continue strengthening his squad ahead of the transfer deadline next week, having already signed 11 new faces at the Stadium of Light this summer.
But Rennes are also in the market for a left-back and Sunderland face a battle to persuade the defender to switch France for the Premier League.
The Senegal international, who switched allegiance from France U-21s to Senegal in 2011, has spent 17 years with Toulouse and it is thought he would prefer to remain in Ligue 1.
M’Bengue has twice been at the centre of controversy in France. He was banned for 13 matches by the French Football Federation in 2007 after seriously injuring a Monaco player when playing in the Championnat de France amateur league, which is the French reserve league.
Just two years later the defender was banned for almost three months after another serious challenge, this time against Monaco’s Alejandro Alonso when playing in Ligue 1.
M’Bengue has made over 130 appearances for Toulouse since breaking in to the first-team in 2007, scoring two goals, and he has represented Senegal on 10 occasions.
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