Greece will have to commit to additional fiscal measures for the aid to kick in, said the source, who requested anonymity because the ministers had agreed to keep confidential the result of the conference call they held on Wednesday.
The European Commission will design and coordinate the package, drawing on the expertise of the ECB and the IMF, the source said, adding that the ministers were unanimously against asking the IMF for financial help.
Euro area member states will take determined and coordinated action, the source said, quoting the finance ministers agreement in the call, which laid the groundwork for an EU summit later on Thursday.
Austrian Chancellor Werner Faymann earlier on Thursday told Austrian radio ORF he expected an aid package for Greece to be a combination of IMF involvement and loans by EU countries.
We are not talking about a donation or subsidies, we are talking about loans with interest which we provide to help a country in order to avoid irritations on financial markets and crises nobody can handle anymore, Faymann said.
We don't know yet how it will be organized, but I expect it will be a cooperation between (EU member) countries and the IMF, he told ORF's morning news show on Thursday.
Faymann said it was important for the EU to stop the Greek crisis from spreading further through the European Union.
Once financial markets are calmed down, the central bankers say there won't be a brushfire, and if we stop it at the first instance, it will have a bigger impact than if we just bury our heads in the sand, he said.
(Reporting by Boris Groendahl; Editing by Mike Peacock)