In a major victory for U.S. labor unions, the National Labor Relations Board made it easier Wednesday for the growing legion of temporary workers to join unions at the companies to which they are assigned.

          Many of the nation's 35 million temporary workers will be able to join company unions, putting them in a position to bargain for medical benefits and other compensation, as a result of a ruling Wednesday by the National Labor Relations Board. The decision by the labor board, an independent federal organization, will primarily affect those workers on longer-term assignments, rather than temporary workers in short-term jobs.

          Only temporary workers who are supervised by company employees are eligible, and the worker would be allowed to bargain with both the temp agency and their assignment company.