At an economic forum in Paris, Coeure said the ECB had acted to prevent the break-up of the euro by agreeing its new bond-purchase program, dubbed Outright Monetary Transactions (OMT).

OMTs aim "to price out a type of catastrophic risk premium that investors demand in conditions of market paralysis," Coeure said in the text of a speech for delivery at the forum.

"It was breakdown risk in the early stage of the crisis, the risk that the payments system would seize up completely. It is break-up risk now," he added.

The ECB will do everything within its mandate "to ensure price stability in the euro area and therefore trust in the euro as a currency," he said.

But he added that the euro zone needed closer political cooperation to coordinate crisis management policies.

"The notion that the euro is a currency without a state is in my view misguided," he said. "The euro is a currency with a state - but it's a state whose branches of government are not yet clearly defined."

Former ECB President Jean-Claude Trichet's idea for a euro area Treasury would be an important step in bringing greater clarity to the role of government in the bloc, Coeure said.

"The ECB is independent and fully accountable, but it needs clearly identifiable and fully empowered interlocutors," he added.

(Reporting by Lionel Laurent; Writing by Paul Carrel, Editing by Gareth Jones)

• A Permanent Economic Emergency