Several decades after their leaders blew their last chance the workers of the world have the opportunity to unite once again.

Or maybe that should be Unite [2] - as the UK trade union of that name, and America's United Steelworkers [3] (USWA) announce a formal alliance at the USWA annual conference.

And Unite has been extending its links in other directions too: there have been talks with the Australian Workers' Union (AWU), and the union is also in touch with several of its European counterparts. If all goes to plan, the new, as-yet-unnamed organisation, with a membership of over three million, will be the first truly international union since the heyday of the Industrial Workers of the World (IWW) [4], more affectionately known as the Wobblies, in the 1930s.

According to Derek Simpson, Unite's general secretary, the aim is to create a union which is as global as the companies its members work for. Much of the plan is still at the broad-brushstroke stage; Simpson's explanation is that the agreed alliance between Unite and USW is “not exactly a merger".

"Effectively, we're setting up the shell of a global union, and eventually both organisations will transfer into it.” Unite and USW plan to have two co-chairmen and, if the AWU or European counterparts join, “the model is designed to expand”.

Overall reactions to the plan have been positive. Owen Tudor, the TUC's international relations officer, feels “it's hard to see a downside at a time when capitalism is globalised and working across national boundaries”. And he's unworried by the fluidity of arrangements between the unions so far. “They seem to be focused on the politics first, rather than on creating an organisational structure and fitting the politics around it. I think that's the right way to start out.”

Others, while showing general support for the idea, foresee difficulties. One issue is the structure of Unite, which was created last year by a merger between T&G and Amicus – a union which itself was an amalgamation of several smaller organisations.

“Part of the problem is that Unite covers everything and nothing, really. It doesn't have a lot of significant sector-level monopolies on members,” points out Richard Hyman, professor of industrial relations at the London School of Economics. So the planned global union would still have to negotiate common policies with other organisations. And since the unions were all created along national lines, “they represent distinctive, national interests. In many industries, there is an underlying international competition in terms of investment and so on. If one is then trying to bargain, competing interests will come to the fore.”

The more fundamental question is whether even a globalised organisation will be able to reinvigorate the fortunes of the trade unions. In the UK, unions now have just half the membership they did 25 years ago, with the financial difficulties that brings, and national mergers have arguably been a form of damage limitation rather than an attempt at meaningful structural reform.

Ian Greer, a research fellow at Leeds University, points out that the alliance between USW and Unite bears the hallmarks of this, as many of the markets Unite operates in are primarily European rather than global. “And the difference is that the European unions are strong - they're not losing members and they don't need to merge.” But Simpson has a different explanation for the partnership. “The US and UK have similar economic climates – they're relatively unregulated, with lots of flexibility to hire and fire labour. European countries work on a social partnership model involving government, employers and unions so alliances have been slower to develop.”

No matter how the global union functions, the chances that it will reprise the power the national unions once had are slim. But the move towards an international alliance is enough of an innovation to give them a fighting chance of survival. As Professor Hyman points out: “Traditionally, the development of these organisations has been nationally blinkered. So anything of this kind is a plus.”