* Cyprus bailout must make debt levels manageable - ECB's Coeure
* There should be no "across the board" bail-in of depositors
* Germany, Finland, others want account holders to bear some costs
* Finance ministers to discuss the package on March 4
FRANKFURT, Feb 27 (Reuters) - Depositors in Cypriot banks should not be forced to take losses across the board as part of a euro zone rescue of Cyprus, ECB policymaker Benoit Coeure said, but he did not rule out making the biggest depositors share some of the burden.
Speaking at a Reuters Summit on the future of the euro zone, Coeure said it was essential to ensure that Cypriot debt is reduced to a manageable level and that the cost of the bailout is fairly shared and not just footed by taxpayers.
The East Mediterranean island has requested up to 17 billion euros ($22 billion) in aid from euro zone partners and the International Monetary Fund because its banks' exposure to neighbouring Greece wiped out their capital base and left the country unable to fund itself.
Germany, Finland and some other euro zone countries are pushing for bank depositors and other investors in Cyprus to carry some of costs of a bailout, both to shield their taxpayers and because of suspicions that wealthy Russians and others have used the island to stash possibly illicit funds.
Opponents of such a move are concerned it could trigger a bank run and further undermine trust in the euro zone, rekindling the worst of the debt crisis. Investors were promised that Greece, where private bondholders were made to accept substantial losses, was a unique case.
Euro zone finance ministers will discuss the package for Cyprus at a meeting in Brussels on Monday, with Germany and France pressing for a decision by the end of March.
"All solutions should be explored," Coeure said. "I wouldn't include a general bail-in of depositors as part of the solution given the risks that it would pose for financial stability.
"So I think the possible bailing-in of depositors across the board is not an option that can be envisaged given this hasn't been done in any country. It would be entirely new and I don't think it's time to make experiments now."
Pressed to say if that left open the possibility of a narrower bail-in of deposits above the EU-guaranteed threshold of 100,000 euros, he said: "There needs to be an appropriate burden-sharing in the programme because we need to achieve debt sustainability. But no bail-in across the board.
"I don't pre-judge any instruments because the vocabulary matters and there are many ways to achieve burden-sharing."
Asked if that was his personal view or that of the ECB board, Coeure said: "I'm pretty sure that (Mario Draghi) is comfortable with the way I've phrased it. No bail-in across the board of depositors."
Having bank account holders bear some of the costs is a risky strategy not only because there is no precedent in the previous bailouts in the euro zone debt crisis, but also because it raises the risk of a run on Cypriot banks.
Cyprus, with a gross domestic product of around 17.5 billion euros, has a bloated banking system with deposits that reached more than 70 billion euros, although latest figures suggest that amount fell in January.
Around a third of the deposits are from non-residents, including many Russian and British businesses.
One proposal for having depositors foot the bill would involve freezing any amounts above 100,000 euros with the total held in an escrow account and used either to shore up the capital of the banks or as collateral for loans.
Cyprus, which elected a new, conservative president on Sunday, is adamantly opposed to the bailing-in of depositors or bondholders, concerned that it will destabilise its already shaky economy and undermine its business model.
But there may be no way to avoid such a move if the European Central Bank, the IMF and the European Commission, together known as the troika, agree that such a step is necessary to make Cypriot public debt manageable.
"Any solution for Cyprus has to be based on a credible debt sustainability analysis, meaning that we have to have the numbers right, we need the programme to be credible from inception," said Coeure.
"I'm not going to enter into the details, there will be a discussion between the troika and the new government."