Bring a large pot of salted water to a boil.

Meanwhile, in a large saucepan or heavy pot, combine clams, 1 cup water, wine and 3 tablespoons oil. Cook over high heat, covered, until clams just open wide, checking frequently after 3 minutes and transferring open clams to a bowl using a slotted spoon. (Discard any clams that remain unopened after 10 minutes.) Strain juices through a fine-mesh sieve into
a bowl; set aside. Reserve 12 clams in their shell for garnish; remove remaining clams from shells; discard shells.

In a large skillet, heat remaining 6 tablespoons oil over medium-high heat. Add onion, reduce heat to medium andcook, stirring occasionally, until just softened, about 3 minutes. Stir in parsley and garlic, then add tomatoes, increase heat to high and cook, stirring once or twice, for 2 minutes. Add clams (both in shells and shelled) and 1 cup reserved clam juices. Remove sauce from heat.

Cook pasta in the boiling water until just under al dente. Drain, then return pasta to pot; immediately add sauce with clams. Cook over high heat, tossing to combine and adding more clam juices to moisten, if desired, for 1 minute. Season to taste with salt and serve immediately.