Mosalem spent last week on trial at Selhurst Park and impressed before returning to his French club Strasbourg.
Warnock has confirmed he has opened talks with a view to signing the 26-year-old, who has made just two appearances in Ligue 1 this season.
"We have spoken to them (Strasbourg) and we are going to see what develops," Warnock told Croydon Today.
"We have to make a move sooner rather than later and we are discussing that at the moment.
"I was impressed by him - he did well."