ATHENS (REUTERS) - Greece's main opposition party leader Vangelis Meimarakis will meet the country's president Prokopis Pavlopoulos on Friday morning to receive a mandate to form a new government, an official from Meimarakis' New Democracy party said.

Given the arithmetic of the current parliament, New Democracy has little chance of pulling a coalition together after Greece's left-wing Prime Minister Alexis Tsipras resigned on Thursday, making national elections the most likely outcome.

Tsipras hoped to strengthen his hold on power in snap elections after seven months in office in which he fought Greece's creditors for a better bailout deal but had to cave in.

Government officials said the aim was to hold the election on Sept 20, with Tsipras seeking to quell a rebellion in his leftist Syriza party and seal public support for the bailout programme that he negotiated. It is Greece's third bailout since 2010.

Faced with a near collapse of the Greek financial system which threatened the country's future in the euro, Tsipras was forced to accept the creditors' demands for yet more austerity and economic reform - the very policies he had promised to scrap when he was elected in January.

"I want to be honest with you. We did not achieve the agreement we expected before the January elections," he told the Greek people. "I feel the deep ethical and political responsibility to put to your judgment all I have done, successes and failures."

His decision to return to the ballot box deepens political uncertainty on the very day Greece began receiving funds under its 86 billion-euro (S$135 billion) bailout programme - five years after a previous government took the first bailout from the euro zone and International Monetary Fund.