Greek Prime Minister George Papandreou sealed a deal with the opposition on a crisis coalition to approve an international bailout, but details remain thin despite an EU ultimatum for Athens to get serious about tackling its huge problems.

With Greece due to run out of money in a few weeks, the European Union told its bickering parties to explain by Monday evening how they would form a unity government to enact the 130 billion euro ($179 billion) emergency funding package.

Papandreou, who sealed his fate last week with a disastrous attempt to call a referendum on the bailout, will stand down when the new government takes over, the office of the Greek president said.

But otherwise he and conservative leader Antonis Samaras came up with the bare minimum to satisfy Brussels, and they must still agree on Monday who becomes the next prime minister to lead a nation which is destabilizing the entire euro zone.

Papandreou's side trumpeted the agreement, reached late on Sunday at talks led by President Karolos Papoulias. 'Today was a historic day for Greece,' government spokesman Ilias Mossialos said, adding that the new coalition would be sworn in and hold a confidence vote within a week, if all went to plan.

Others were less charitable. 'I'm afraid the new government will very soon turn out to be problematic,' said Stefanos Manos, a former conservative finance minister.

The new coalition has to win parliamentary approval for the bailout before calling early elections.

Papandreou's socialist Pasok party and the New Democracy party of Samaras agreed early on Monday that the most suitable date for the elections would be February 19 next year.

Brussels has piled pressure on Athens to approve the bailout, a last financial lifeline for Greece, fearing that its crisis will spill into much bigger euro zone economies such as Italy and Spain - which would be far harder to rescue.

Papandreou and Samaras had been scrambling to reach a deal before finance ministers of euro countries meet in Brussels on Monday evening, to show that Greece is serious about taking steps needed to stave off bankruptcy.

Earlier, European Economic and Monetary Affairs Commissioner Olli Rehn told Reuters that finance ministers from countries that use the single currency would insist on hearing a plan for a unity government from their Greek colleague Evangelos Venizelos at Monday's Eurogroup meeting.

'We have called for a national unity government and remain persuaded that it is the convincing way of restoring confidence and meeting the commitments,' he told Reuters.

'We need a convincing report on this by Finance Minister Venizelos tomorrow in the Eurogroup,' he added.-Reuters