EU finance ministers are set to meet in Brussels to discuss establishing a new "stabilisation mechanism" to prevent the Greek debt crisis from spreading.The fund would reportedly have up to 70bn euros (£60bn) at its disposal to guarantee loans and be available to the 16 member states in the eurozone.
Many leaders want it agreed before markets open on Monday to prevent investor fears over the euro spreading.
But some countries, including the UK, oppose aid on such a large scale.
On Friday, the leaders of the 16 countries that use the single currency approved an 110bn euro ($145bn; £95bn) loan to Greece.
They also agreed to take whatever steps were needed to protect the euro, and to accelerate budget cuts and ensure deficit were cut.
'Watertight defence'
The BBC's Jonny Dymond in Brussels says officials at the European Commission have laboured throughout the weekend to rush through the plans for the European Stabilisation Mechanism.
While bail-outs are banned under EU rules, the commission reportedly plans to extend an existing clause in the Lisbon Treaty originally designed to allow it to provide aid to member states experiencing serious difficulties that was used to help Hungary and Latvia.
Under the plans, the commission would borrow the money for the stabilisation fund directly on the markets, with its own finances guaranteed by EU nations.
Officials hope the loan guarantees would prevent the crisis in Greece spreading to other eurozone countries with high deficits or debts as well as low economic growth, most notably Portugal, Spain and Ireland.
"Between now and Sunday night we will have a watertight line of defence," Eurogroup Chairman Jean-Claude Juncker said on Saturday.
"We have to make it clear that all eurozone countries are ready to defend each and every eurozone country, because they want to defend the eurozone as a whole," he added.
Our correspondent says political acceptance from EU nations is critical, but guarantees would be too much for the UK to swallow.
Deciding the contribution of each country could also be a stumbling block.
Fears that a debt default by Greece could paralyse the world's financial system - just as the collapse of Lehman Brothers did two years ago - caused European, US and Asian stock markets to plunge in the past week.
On Friday, bankers urged the European Central Bank to become the "buyer of last resort" of eurozone government bonds to steady markets.
The president of the European Central Bank, Jean-Claude Trichet, said it had not yet discussed the move but was willing to respond to unfolding events.
The Italian Prime Minister, Silvio Berlusconi, and French President Nicolas Sarkozy have cancelled foreign trips because of the severity of the crisis.
In an interview with Russian media on Saturday, US President Barack Obama said: "I am very concerned about what's happening in Europe. But I think it is an issue that the Europeans recognise is very serious."
