The European Union says it is “relatively close” to a deal with the continent’s banks to write off about half of Greece’s debts, an agreement that could cost the financial institutions about $243 billion.

A spokesman for EU economic affairs commissioner Olli Rehn said Monday that the continent’s leaders “clearly” prefer that the banks reach a voluntary agreement to cut Greece’s $486 billion debt load. But so far EU and bank negotiators have not reached an agreement. The 27-nation bloc is pressing the banks to take a 60 percent loss on their Greek securities, while the banks have been negotiating for a 40 percent cut.

One diplomat said the final figure could “end up somewhere in the middle.”

The intense negotiations over Europe’s debt crisis came as the continent’s leaders ended one summit Sunday and prepared for another Wednesday. They have promised by then to adopt a comprehensive plan to resolve the debt contagion that for weeks has roiled international financial markets and threatened to send world economies into a new tailspin.

Aside from the debt write-off, the EU could require banks to increase their cash reserves by about $139 billion and boost the continent’s bailout fund to assist other debt-ridden countries that could need international assistance in the future.

Irish Prime Minister Enda Kenny said the continent’s leaders realize “the world is watching Europe” and that “there isn’t any point in doing this in a half-hearted fashion.”

European leaders are worried that even if Greece’s debt woes are resolved, other countries, especially Italy and Spain, could be next to next to need outside aid.

German Chancellor Angela Merkel and French President Nicolas Sarkozy, the leaders of Europe’s two strongest economies, pressed Italian Prime Minister Silvio Berlusconi on Sunday to reduce his country’s debt at a faster pace. Italy has already adopted some cost-cutting measures.

French and Greek banks would be among the biggest losers with a write-off of the Greek government debt. Greek banks and pension funds hold about $70 billion of the government’s debts.

Financial institutions holding Greek debt agreed in July to a 21 percent write-off of the securities they hold, but the country’s economic plight has worsened since then, forcing European leaders to call for the banks to assume bigger losses.