During Europe's financial crisis the European Central Bank has been "an anchor of stability and confidence," former president Jean-Claude Trichet told CNBC Friday.
"It is not my working hypothesis there will be a haircut for the ECB," he said.
Greece is "part of a system of the advanced economies," and the European Union governments "had said clearly what they are aiming at," so they should stick to the plan.
"Deliver comprehensively, immediately and effectively what you have decided," he said. "The problem is confidence. The decision, the orientation, the direction is good, but you have to deliver as soon as possible [and] as convincingly as possible because confidence is of the essence."
He said he can understand that during a time of crisis some European banks are "ringfencing," or only lending within their own countries.
"I see the rationale behind it," he said. But the long-term goal is a single European market, "and that means decoupling the financial sector from the sovereign debt ... Let's not embark on a generalized renationalization of the financial sector. We have to do what is required by the crisis but never lose sight of the medium and long-term perspective."