In a large bowl, dissolve yeast in warm water. Add the sugar, salt and 3 cups flour. Beat on medium speed for 3 minutes. Stir in remaining flour to form a soft dough., Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease the top. Cover and let rise in a warm place until doubled, about 1 hour., Punch dough down. Turn onto a floured surface; divide in half. Shape each portion into a loaf. Place each loaf seam side down on a greased baking sheet. Cover and let rise until doubled, about 30 minutes. , Meanwhile, preheat oven to 400°. With a sharp knife, make four shallow slashes across top of each loaf. Bake 20-25 minutes or until golden brown. Remove from pans to wire racks to cool.