German Economy Minister Philipp Roesler expressed disappointment with the efforts of debt-wracked Greece to implement necessary reforms, in an interview with the weekly magazine Focus.
"I've lost my illusions," said Roesler, who is also vice chancellor and leads the pro-business Free Democrats in Germany's ruling coalition.
"I proposed with German businesses a whole series of support measures for the Greek government. The Greeks have hardly responded to our offers," he told Focus according to an advance copy of an article to appear in its Monday edition.
On July 22 Roesler had voiced his doubts concerning the possibility of Greece staying in the eurozone, saying that in his view there had been "nothing frightening" about a Greek exit "for a long time".
The next day the German government said it was torn between hope and scepticism about Greece's ability to meet its commitments to its international creditors.
The responsibility for managing the debt crisis for Germany however rests with Finance Minister Wolfgang Schaeuble, not Roesler.
Germany, Europe's biggest economy, is now waiting with its eurozone partners for the auditors' report on Greece, which will determine if Athens receives the next tranche of 31.5 billion euros as part of its second bailout. The report is expected by mid-September.