Heat oil in pot set over medium-high heat. Add onions and garlic and cook 3 to 4 minutes. Add wine, diced tomatoes, tomato paste, oregano and sugar. Simmer 5 minutes. Add sausage and clams. Cover and cook until clams just open. Season to taste and serve.
Note: Discard any clams that do not close when squeezed before cooking, or that do not open after cooking.