Asked about financial market regulation, Schäuble said late Wednesday: "Of course it would be better on a global level and if it doesn't work at a global level, then at a European level, and if that doesn't work, then at a national level. That goes also for a tax on financial transactions."
In September, Europe went ahead with landmark proposals to tax the financial sector, ignoring US opposition in a move that also provoked grumblings in London which fears capital flight from the City.
The idea of a tax on financial market transactions has been pushed hard by German Chancellor Angela Merkel and French President Nicolas Sarkozy. The plan will likely be discussed at a summit of all 27 European Union heads of state and government at an October 23 summit, and also be put to a summit of G20 leaders in Cannes on November 3-4.
European Commission president Jose Manuel Barroso has said the tax could generate around €55 billion ($76 billion) a year.
Speaking to members of Merkel's conservative Christian Democrats, Schäuble also insisted that Greece's debt needed to be reduced to a more sustainable level.
"If Greece's debts are not sustainable in the long-term - and it seems that they are not - they need to be reduced to make them sustainable and that's what we have been discussing in recent days," he said. "I know that the markets do not like that, but there is no alternative."
He added that private investors must take heavier losses in a second bailout plan for Greece, without mentioning a level for such a write-down, as speculation swirls of a "haircut" as high as 60 percent.