Prime Minister David Cameron is set to join other European leaders to decide measures to prevent Europe's financial crisis from spiralling out of control.Ahead of the meeting in Brussels, German Chancellor Angela Merkel said she believed the leaders will devise a plan by Wednesday to protect the euro.A deal on how to recapitalise banks was reached by ministers on Saturday.UK chancellor George Osborne said Britain would keep up the pressure to resolve the crisis.All 27 EU leaders are meeting on Sunday morning, and then in the afternoon the countries that use the euro will hold a special summit of their own. This will then be followed by another meeting on Wednesday.The BBC's Europe correspondent Chris Morris said the meetings were an indication of how much still needs to be decided.He said: "Everyone now acknowledges that previous decisions on a second bail-out for Greece are insufficient."Far more of its debt will have to be written off, and that means banks and other financial institutions will have to take a much bigger hit. But how much debt, and how big a hit?"The provisional deal agreed by finance ministers will see banks raise more than 100bn euros (£87bn) in new capital to shield them against possible losses to indebted countries.It is conditional on a wider accord, including a write-down of Greek debt.BBC business editor Robert Peston said the 100bn euros agreed in the deal will be provided to banks by commercial investors, national governments and the EU's bailout fund.Speaking after the 10-hour meeting on Saturday, Mr Osborne said: "Britain will keep up pressure in the next few days to a comprehensive package to resolve the European crisis and to make sure that we get jobs and growth."Debt-addled Greece has been bailed out - twice - along with the Irish Republic and Portugal.The eurozone is working on a third package for Greece, as well as a solution that could help the huge-but-faltering economies of Spain and Italy.