Aaron Pressman, reporting for Fortune: Some 21,000 workers in AT&T's wireless business have overwhelming voted to authorize a strike just ahead of the expiration of their contract on Saturday. The vote, which was expected, comes after 17,000 additional workers in AT&T's phone, internet, and cable services in Nevada and California also approved a strike authorization last month. They have been working without a contract since April. But despite the strike authorization votes -- a common tactic to increase pressure on management during labor negotiations -- AT&T said it was still seeking to find common ground with its workers. Unlike some of its peers, AT&T has had a long run of labor peace with its workers and their main union, the Communications Workers of America (CWA).