ATHENS (Reuters) Greek opposition politicians embarked on the laborious and apparently futile exercise on Saturday of trying to form a new government, oblivious to pressure for rapid elections so the nation can start tackling an array of crises.

The two biggest opposition parties, one of the center-right and the other of the far left, queued up to exercise their constitutional right to spend three days negotiating a new coalition, even though their efforts are almost certain to fail.

When leftist Prime Minister Alexis Tsipras resigned on Thursday, he had in mind a quick election next month when he hoped to return to power, strengthened by a mandate to implement the new bailout program he negotiated to save Greece from financial collapse.

But the conservative New Democracy and the anti-bailout Popular Unity - founded only on Friday after splitting from Tsipras' Syriza party - do not share his sense of urgency.

Fofi Gennimata, who leads the small PASOK socialist party, reminded fellow opposition leaders that Greece's future in the euro zone was far from secure, even though funds began flowing from the new 86 billion euro ($98 billion) bailout on Thursday.

"It is obvious that ... this parliament cannot form a new government. Therefore, any delay can have destructive consequences for the country because, as I have said many times, Grexit remains in our backyard," she told reporters after meeting conservative New Democracy leader Evangelos Meimarakis.

Meimarakis was also due to meet leftist Popular Unity chief Panagiotis Lafazanis - his ideological polar opposite - later on Saturday. The two are also split over the bailout, with Meimarakis backing the deal which this week averted a debt default and Lafazanis saying "we will either finish off the bailouts or the bailouts will finish off Greece".

Even if they could come to terms, the two parties would command only 101 seats in the 300-member parliament, with the rest of the deeply divided opposition ranging from communists to the ultra-right Golden Dawn.

If Meimarakis fails, then Popular Unity will get three more days to have a go. This raises the possibility that Lafazanis might invite Meimarakis back for presumably much the same conversation all over again.

Tsipras still leads by far the biggest party in parliament - Syriza had 149 seats before the 25 anti-bailout rebels under Lafazanis walked out - and he has yet to meet any opposition leader. In any case, he is highly unlikely to want a coalition deal as he pursues his ambition of governing alone, quite apart from the fact Meimarakis has called him a "bit of a fibber".


Meanwhile pressure is growing at home and abroad for urgent action during what Tsipras has called a crisis within a crisis. On top of implementing the bailout program and rescuing the banks, Greece is struggling with a humanitarian crisis.

Many thousands of refugees from the Syrian civil war and other migrants are massed on Greek islands, having crossed in small boats from Turkey. Others are trapped on the northern border with Macedonia in filthy and squalid conditions, with the Greek government saying it has no money to help them.

"Implementing the accord reached with the lenders, recapitalizing the banks and the migrant crisis are burning issues that cannot wait, not even one month," said the conservative Kathimerini newspaper.

In October Greece has to pass a review by the euro zone and the International Monetary Fund of how it is implementing promises of yet more austerity and economic reforms. Failure could mean a halt to funding, threatening a financial collapse and possible exit from the euro that was averted only narrowly when Tsipras caved into the creditors' demands.

Europe appears apprehensive about the prospect of political paralysis.

Tsipras spoke to French President Francois Hollande by telephone on Friday. Jeroen Dijsselbloem, who chairs meetings of euro zone finance ministers, urged Greece to hold elections as soon as possible to avoid delays in implementing the bailout.

If none of the three biggest parties - Syriza, New Democracy and Popular Unity - can form a coalition, President Prokopis Pavlopoulos could call elections as early as the middle of next week, to be held within 30 days.

(writing by David Stamp; editing by Gareth Jones)