The Scottish international, who travelled to France with Paul Hart's squad last week, is expected to join Forest over Division One rivals Burnley.
Stewart's agent George Wright told skysports: "There's still a bit of work to be done, but if an agreement is made and everything is fine he'll stay with Forest for the whole season."
Burnley were interested in Stewart but have taken Luke Chadwick on loan after impressive performances for Reading in Division One last season.