The long-discussed merger between Pittsburgh's United Steelworkers and Britain's Unite, creating the first transatlantic "super" union, is being called an important step in labor's global strategy, allowing workers to better negotiate with the sophisticated multinational corporations that employ them.

The self-proclaimed counterforce to corporate globalization may soon target mergers with labor groups in the emerging economies of Asia, Latin America and Eastern Europe. Together, the two unions already represent workers in the U.S., Canada, the Caribbean, Ireland and the United Kingdom, and are in talks to take on the Australian Workers Union.

The merger, the two unions say, will differ from the loose alliances that USW has been building since the 1990s, as steel production moved out of America and into lower-cost labor markets. While the two unions will still operate independently, when need be, they will join at the top of the organization for membership drives and negotiations with common employers.

"There are really no American companies any longer," said Wayne Ranick, USW spokesman. The big companies that we think of as being American, "all of them are multinational," often with a presence overseas.

"Right now, there is no countervailing force to global capital," Mr. Ranick said.

Officials from USW and Unite, with more than 2 million members in transportation, energy and other sectors, met last week in London and, according to published reports, put the "finishing touches" on a merger that had been discussed from the moment Unite was formed a year ago through an alliance of the Amicus and the Transport and General Workers Union, both from the U.K. The merger terms have been endorsed by Unite officials, and USW will discuss the plan at its annual conference in July.

The union will have co-presidents at first, with USW president Leo Gerard keeping his leadership role. Eventually the union will have a single leader, according to a Wall Street Journal account.

As the industrial and manufacturing sectors, which traditionally are heavily unionized, have declined in America, USW has padded its roster to 850,000 (1.2 million, including retirees) by absorbing unions from other sectors, to the point that steelworkers now account for about one-fifth of the workers represented by the USW. Still, it takes on manufacturing workers when it can -- last year, USW merged with the Independent Steel Workers Union.

That merger, like this one, was about boosting the USW's bargaining leverage in an era when consolidations, international mergers and private-equity buyouts are the routine.

But will the strategy be effective? How would a super union with global designs operate on behalf of members, especially manufacturing workers, who have been accused historically of being too protectionist and parochial? Can the labor movement really reverse its slide by reaching globally when the phenomenon of global capital has such a big head start?

Labor weakness "is a global phenomenon ... I do not believe you can merge or acquire your way out or fundamental problems," said Marick Masters, labor expert and business and international affairs professor at the University of Pittsburgh.

"The big worry that I have about this type of merger is, how do you represent such a diverse body of workers?"

USW has been doing that for years, though. Since its creation in the 1940s, USW has grown primarily by merging with smaller unions. Recently, the USW has absorbed the 55,000-member Industrial, Wood and Allied Workers of Canada (2004), and the 275,000-member Paper, Allied-Industrial, Chemical and Energy Workers International Union (2005). No longer are steelworkers the primary focus of United Steelworkers, despite its namesake and its Pittsburgh headquarters.

"Loss of focus is a concern," said Harley Shaiken, labor professor at the University of California Berkley. "But I think it's trumped by the increased leverage that the union gains" from its improved resources and larger geographic footprint.

When pitted against multinational companies, "bargaining simply in a single country puts you tactically at a disadvantage," Mr. Shaiken said.

Whether or not the "super" union experiment is destined to succeed, other unions are expected, or already trying, to follow suit. For years, the Service Employees International Union and its 1.9 million members have been building a loose global network of security guard and janitorial unions, negotiating on their behalf in other countries.