SIOUX FALLS, S.D. (AP) — The union at a Smithfield Foods pork processing plant in South Dakota has begun contract negotiations armed with the authorization to call a strike. The strike authorization at the Sioux Falls chapter of the United Food and Commercial Workers Union was overwhelmingly approved late Monday with 98% of the vote total. However, union leaders say they hope to avoid a work stoppage as they prepared for a meeting with company representatives Tuesday. The union is demanding that Smithfield boost its wage offerings. Virginia-based Smithfield Foods says its initial contract offer was in line with accepted agreements at other plants.