Karl-Otto Pohl, former president of Germany's Bundesbank, tells BBC1's Panorama programme tonight that a postponement would be the end of the plan to join Europe's currencies in a monetary union. But he adds that the economic problems facing France and Germany mean this could be inevitable.
One of the most prominent German public figures to come out against the single currency, he says: "If unemployment is rising further and the recession is getting deeper, there could be a situation where they have no choice, where they have to accept a delay."
In an interview that will delight Britain's Euro-sceptics, Mr Pohl argues that the European Union is a post-war concept which is now out of date. However, the German Chancellor, Helmut Kohl, repeats his warning that European unity is the only way to avoid another war.