Saab has halted development of the next-generation 9-3 while company strategists consider a plan to build the new model on a smaller platform.GM insiders say that pressure from upcoming fuel economy and CO2 emission regulations in Europe and the US have forced Saab - and owners General Motors - to look at radically downsizing the model.The new 9-3 may be built on a version of GM’s upcoming ‘Global premium compact’ platform, said senior Saab sources. This chassis also underpinned the Saab 9-X concept shown at February’s Geneva show and is likely to peg the new model’s length at 4.5m.If these plans are given the green light by GM bosses, it will be one of the first concrete examples of new emissions regulations radically influencing future model development.Under GM’s original plans, the third-generation 9-3 was set to based on the new Epsilon 2 chassis (which also underpins next year’s new Saab 9-5 and the Vauxhall Insignia). This chassis is substantially longer and wider than the current Epsilon one.One GM design source told Autocar that there were a number of new technologies that could be applied to a smaller chassis to maximise interior space. These included a slim ‘modular’ roof assembly to increase headroom, as well as slimmer doors in conjunction with new side-impact technology to improve cabin width.Over the next couple of years Saab’s Trollhatten factory will be refitted to build cars based on the Global Compact Premium chassis, opening the way for Saab to manufacture both its upcoming Audi A3-rivalling 9-1 model and the new 9-3 in Sweden.However, there’s also a strong chance the 9-3 could also be built at a GM factory in the US. This is because exporting cars from Sweden to the US is a near profit-free exercise because of the strength of the Swedish krona against the weak US dollar. The 9-3 was originally scheduled to be built at Opel’s Russelsheim plant in Germany, alongside the new 9-5 and Insignia.Saab’s downsizing plans emerged when the unions at the German factory asked GM why the new 9-3 had not yet been confirmed for production in Germany.