Celery, Potato and Chicken Skillet Stew

1 pound red-skinned potatoes -- cut in 3/4"

2 cups sliced celery -- divided

1/2 cup celery leaves, chopped -- divided

1 tablespoon vegetable oil

12 ounces boneless skinless chicken breast

cut into 1" ieces 1 cup red bell pepper -- chopped

3 tablespoons tomato paste

1/2 teaspoon dried rosemary leaves -- crushed

1/2 teaspoon sugar

1/4 teaspoon black pepper

salt

Bring 1 qt. water to a boil in med. saucepan over high heat. Add potatoes, 1 cup celery and 1/4 cup celery leaves. Reduce heat to med.; simmer, covered 7-8 min. or until potatoes are tender. Drain, reserving cooking liquid and vegetables separately. Heat oil in large nonstick skillet over med.-high heat. Add chicken, bell pepper and remaining 1 cup celery. Cook, stirring constantly, 6-7 min., or until chicken is no longer pink. Stir in tomato paste, rosemary, sugar, black pepper and 2 cups reserved celery liquid. Bring to a boil; cook until sauce thickens, about 4 min. Add reserved potatoes and celery. Season to taste with salt. Sprinkle with remaining celery leaves.