Rangers Set Up Cuellar's Replacement?
Real Betis failed with a bid for the Algerian international last month as they came up short of Charlton's valuation.
Betis are understood to have bid £1.6million but it is believed The Addicks want at least £2.5million for the central defender.
The 25-year-old moved to the Valley just over 18 months ago and he has become a huge fans' favourite.
But his displays have attracted interest from elsewhere with Rangers now joining the hunt.
However, there is also Premier League interest in the African stopper.