By Robin Emmott and Ingrid Melander LUXEMBOURG (Reuters) - The European Union sought on Friday to forge rules to force losses on large savers when banks fail, a divisive reform that will shape how the euro zone deals with its sickly lenders. Finance ministers in Luxembourg are trying to resolve one of the most difficult questions posed by Europe's banking crisis - how to shut failed banks without sowing panic or burdening taxpayers. "We are in for a very tough negotiation," Sweden's Finance Minister Anders Borg told reporters as he arrived for the meeting, saying a one-size-fits-all rule for all EU countries was "dangerous." The European Union spent the equivalent of a third of its economic output on saving its banks between 2008 and 2011, plundering taxpayer cash but struggling to contain the crisis and - in the case of Ireland - almost bankrupting the country. But countries are divided over how strict the new rules should be, with some worried that imposing losses on depositors could prompt a bank run while others argue the rules of the game must be made clear from the start. While there is no immediate deadline for a deal, dithering could undermine confidence in the ability of Europe's politicians to repair the financial system, encourage banks to lend again and help the continent emerge from its economic stagnation. "Midsummer is the longest day of the year so we have plenty of time," said Olli Rehn, the European Commission's top economics official, referring to the northern hemisphere's June 21 summer solstice. A 300-page draft EU law that forms the basis of discussions recommends a pecking order in which first bank shareholders would take losses, then bondholders and finally depositors with more than 100,000 euros ($132,000) in their account. That would make the harsh treatment of savers that was part of Cyprus's bailout in March a permanent feature of Europe's response to future banking crises. The rules to impose losses on savers, whether wealthy individuals or companies, could be made stricter within the euro zone, in particular for banks seeking help from the single currency's rescue fund. Although not part of the same project, common rules in the wider European Union are considered a stepping stone towards the euro zone's banking union. Euro zone finance ministers agreed late on Thursday to set aside 60 billion euros to help banks via the fund, the European Stability Mechanism, but with tough conditions. Still, the idea divides countries with big banking sectors who have the most at stake in any financial crisis. Sweden, Britain and France say countries should have the final word in deciding how to close banks and not be tightly bound by any new EU rules. While Sweden is adamant it must have as much control as possible over how it deals with its banks, France's Finance Minister Pierre Moscovici signaled Paris is open to compromise. "France wants flexibility but it is willing to agree to some limits," Moscovici said. Nothing is insurmountable. For the policy draft on direct bank recapitalization, see here Additional reporting by Martin Santa, Ethan Bilby; writing by John O'Donnell and Robin Emmott; Editing by John Stonestreet