The Dutchman has not played since returning from the World Cup in South Africa with a torn hamstring.
"He's very good in training and he feels absolutely no pain," said van Gaal.
"He's very impatient to play, it's normal after six months out, but he has to wait until January 15."
Robben will feature in a friendly against a German regional side on January 12 and if he holds up will play for up to 30 minutes against Wolfsburg.
But van Gaal ruled out the 26-year-old playing during Wednesday's German Cup tie against Stuttgart. "If I do that I think that Dr. Muller-Wohlfahrt would have a heart attack," joked the Dutch coach.