Mix condensed milk, cinnamon, ginger and nutmeg with whisk until blended.
Sprinkle gelatine over water in medium saucepan; let stand 1 min. Cook on low heat 2 min. or until gelatine is completely dissolved, stirring constantly.
Add milk mixture; stir until blended. Continue cooking 5 min. or until slightly thickened.
Remove from heat. Stir in pumpkin. Spoon into crust.
Refrigerate 4 hours or until firm. Top each serving with a dollop of COOL WHIP just before serving.