Manhattan Clam Chowder

1/4 cup margarine or butter
1 small onion, finely chopped
2 cans minced or whole clams, drained (reserve liquid)*
2 cups finely chopped potatoes
1 cup water
1/3 cup chopped celery
2 teaspoons snipped parsley
1 teaspoon salt
1/4 teaspoon dried thyme leaves
1/8 teaspoon pepper
1 (16 ounce) can tomatoes, undrained

Cook onion in margarine or butter in Dutch oven until onion is tender. Drain clams, reserving liquid. Stir clam liquid, potatoes, water and celery into onion. Cover and cook until potatoes are tender, about 10 minutes. Stir in clams and remaining ingredients. Break up tomatoes with fork. Heat to boiling, stirring occasionally.

* 1 pint shucked fresh clams with liquid can be substituted. Chop clams and add with the potatoes.