"I'm somewhat sceptical whether that'll be possible by Monday. But I'm not ruling it out," Schäuble said referring to an upcoming meeting of the "Eurogroup" of eurozone finance ministers which will discuss releasing a new tranche of bailout aid to Athens.
Greece needs a deal to unblock €7.2 billion euros from its EU-IMF bailout before state coffers run dry.
Alexis Tsipras' hard-left government, elected in January on an anti-austerity agenda, is struggling to pay salaries and pensions without the promised loans.
Greece needs to repay almost a billion euros in debt and interest to the IMF by May 12.
The European Union and International Monetary Fund want Athens to carry out reforms pledged by previous administrations before it releases the final tranche of rescue funds.
But the Greek government insists it will not back down from 'red lines' on labour protection and wage cuts.
Schäuble said that "too much time has been lost already."
He insisted that Germany, like the other eurozone countries, was prepared "to do everything to help Greece within the framework of what was agreed."
"We don't like to speculate about a 'Grexit'" or Greek exit from the euro, Schäuble continued.
"We don't want that. But that doesn't mean we're prepared to do absolutely anything. Athens has perhaps wrongly assumed that," he said.
Schäuble warned that Greece's liquidity "has clearly diminished. And that means anything could happen."
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