EU finance ministers have agreed on emergency measures worth 500bn euros (£430bn) to prevent the Greek debt crisis from affecting other countries.
The 16 members of the single currency bloc will have access to 440bn euros of loan guarantees and 60bn euros of emergency European Commission funding.
The International Monetary Fund (IMF) will also contribute up to 220bn euros.
Economic Affairs Commissioner Olli Rehn said the agreement "proves we shall defend the euro whatever it takes".
There had been fears that without the measures, the euro might have come under heavy pressure on financial markets as investors grew concerned about financially-troubled states such as Portugal.
The euro has strengthened in early trading in the Far East, surging above $1.29.
Marathon talks
Speaking early on Monday following 11 hours of talks, Spain’s Finance Minister Elena Salgado announced that an agreement had been reached on a package to defend the euro and eurozone economies.
Under the aid plan, the European Commission would make 60bn euros available while members of the eurozone would promise bilateral backing for 440bn euros of loans and guarantees, she said.
The IMF would contribute an additional sum of at least half of the EU’s contribution, or 220bn euros, Ms Salgado added.
Mr Rehn said the European Central Bank (ECB) would also take exceptional market intervention measures, thought to be the purchase of eurozone government bonds.
"The fiscal efforts of the EU member states, the financial assistance by the commission and by the member states, [and] actions taken today by the ECB proves we shall defend the euro whatever it takes."
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