Place tomatoes, oregano and 2 tbsp of water in a medium saucepan. Simmer until the tomatoes are sauce-like (10-15 mins). Meanwhile, brown the chicken, garlic and onion in an oiled frying pan until the meat is cooked through, set aside. Add the green pepper, soy sauce, bouillon cube and sugar to the tomato sauce, cook an additional 3-5 mins or until green peppers are tender-crisp. In a small bowl, mix the flour and remaining water. Add to the sauce and heat through until slightly thickened. Add chicken. Serve over warm pasta.