"The promises from Greece aren't enough for us anymore,» Schaeuble said. «With a new austerity programme they are going to first have to implement parts of the old programme and save."
Schaeuble pointed out that German opinion polls show a majority of Germans are willing to help Greece.
"But it's important to say that it cannot be a bottomless pit. That's why the Greeks have to finally close that pit. And then we can put something in there. At least people are now starting to realize it won't work with a bottomless pit."
Schaeuble said Greece would be supported «one way or another» but warned the country needed to do its homework on improving its competitiveness and hinted it might have to leave the euro zone to do that.
"Greece needs to do its own homework to become competitive -- whether that happens in conjunction with a new rescue programme or by another route that we actually don't want to take..."
When asked if that meant Greece would leave the euro zone for that, Schaeuble said:
"That is all in the hands of the Greeks themselves. But even in the event (Greece leaves the euro zone), which almost no one assumes will happen, they will still remain part of Europe."
Schaeuble said Germany, the euro zone's paymaster, wants to prevent that.
"We're happy to help but we shouldn't give others the feeling that they don't have work hard themselves. Every country is responsible for itself."
He said that the rescue efforts for Greece are turning out to be more difficult than efforts associated with German reunification in 1990.
"The reason is the realization that there is a need for change, and change dramatically, still needs to develop further with a lot of people in Greece,» said Schaeuble, who was a key government architect of German reunification.
Schaeuble said there was quite a difference between Greece and other euro zone strugglers.
"The Greeks are a special case...The Portuguese government is doing a decent job,» he said, adding that Portugal's problem is that the country needs more economic growth.
"Our goal is to help give Greece a future by making it fit and competitive so that the people there have their chances,» he said. «But the path is going to be difficult."