Dire Warnings

More dire warnings rained down on the Greek leader as he contemplated what concessions to make to clinch a deal without alienating his left-wing supporters who elected him in January on promises to put an end to years of austerity.

"There is a strong determination to help Greece," Weidmann said in a speech in London. "But time is running out, and the risk of insolvency is increasing by the day."

The main losers of a Greek default and euro exit would be Greece and the Greek people, he said.

The Greek leader faces pressure both from left-wing hardliners and from voters, most of whom say they want to remain in the euro zone and want him to make concessions for a deal.

Underlining the resistance Tsipras faces if he gives too much ground, hundreds of supporters of the Communist-affiliated trade union PAME flooded on to an Athens square in a peaceful anti-bailout protest on Thursday evening.

Earlier they replaced the EU flag with PAME's on the roof of the finance ministry. They also draped a banner across five storeys of the ministry showing two previous prime ministers who each negotiated a deal with the lenders. Next to them was a portrait of Tsipras above the slogan "Bailout Number Three".