Ten thousand grocery store workers could go on strike against three St. Louis-area grocery store chains as early as next week. They have rejected a four-year contract offer form Schnuck Markets, Dierbergs Markets, and Shop n’ Save Warehouse Foods. Members of the United Food and Commercial Workers Local 655 will hold a strike vote next Tuesday. If the strike proposal fails to get a two-thirds vote, the contract takes effect. A union spokesman says workers are upset at small wage increases and higher health care costs. The labor dispute affects 57 Schnucks, and 21 Shop ‘n Save stores and 11 Dierbergs. The grocery store companies say their proposal allows them to stay competitive with nonunion competitors such as Wal-Mart, Costco, and Walgreen.