A noisy crowd, estimated at around 2,000 people, gathered outside the presidential palace in the early evening, far more than the hundreds who had gathered there in recent days. With flanks of riot police standing guard, many demonstrators chanted, “Resign! Resign!” as they inveighed against the imminent consolidation of the Laiki Bank, one of Cyprus’s biggest and most troubled lenders. In a move demanded by the I.M.F., which will cost thousands of jobs, the toxic assets of Laiki will be hived off into a so-called bad bank, while healthy assets and accounts will be moved to the Bank of Cyprus. There, accounts over 100,000 euros would be subject to the 20 percent tax.

A cutoff of central bank financing and the absence of a bailout agreement could cause Cypriot banks to collapse. It could also lead to a disorderly default on the government’s debt, with unpredictable repercussions for the euro monetary union, despite the country’s tiny economy.

Asked on Saturday whether Cyprus had a backup plan if a deal is not reached, a government spokesman, Christos Stylianides, said, “We are doomed” if a solution is not found.

Olli Rehn, the European Union commissioner for economic and monetary affairs, said in a statement on Saturday evening that it was “essential that an agreement is reached by the Eurogroup on Sunday evening in Brussels.”

But Mr. Rehn also suggested that opportunities had been squandered to find a less painful way out of the crisis. In a thinly veiled reference to the Cypriot Parliament’s rejection of an earlier deal, Mr. Rehn that “the events of recent days have led to a situation where there are no longer any optimal solutions available” and that, “Today, there are only hard choices left.”

European Union leaders “may conclude that it is best to let Cyprus default, impose capital controls and leave the euro zone,” Nicolas Véron, a senior fellow at Bruegel in Brussels and a visiting fellow at the Peterson Institute for International Economics, said in a recent assessment. “But such a move would violate the promise of European leaders to ensure the integrity of the euro zone no matter what and potentially set off a chain reaction, including possible bank runs in other euro zone member states, starting with the most fragile ones, such as Slovenia and, of course, Greece.”

Parliament was still deciding when to vote on the new proposal to tax uninsured bank deposits.

The finance ministers and the troika on Saturday were still calculating how much money those deposit-tax alternatives would raise for the government.