It's about "providing a credible public backstop at the European level capable of reassuring supervisors and market participants that financial stability will be assured," O'Connor said.
O'Connor stressed a decision was needed ahead of the European Central Bank's review of banks' balance sheets early next year. The ECB will carry out the review as it prepares to become the central regulator for the EU's biggest banks in late 2014.
The review, complete with a stress test to see how banks would fare in times of trouble, is likely to identify capital shortfalls worth billions of euros, if not dozens of billions, analysts say. Banks will primarily seek new capital on the markets, but if that proves unviable governments will have to step in.
While Britain, which is also home to the bloc's biggest financial industry, would certainly be capable to plug any capital shortfalls on its own, governments in smaller economies with a weaker financial position, like Hungary or Romania, might struggle to raise sufficient capital.
The EU's balance-of-payments fund currently has about 40 billion euros left of its initial firepower, after granting assistance to Latvia, Hungary and Romania since 2010.
Tapping the fund requires countries to apply and to accept tough conditions, just as eurozone nations must commit to reforms and budget discipline to qualify for ESM aid.
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