There is still a "major issue of trust" between the Greek government and its international creditors, the head of the eurozone's finance ministers said on Saturday.
Speaking ahead of late-night discussions, Dutch Finance Minister Jeroen Dijsselbloem, the Eurogroup president, said: "There is, of course, a major issue of trust: can the Greek government actually be trusted to do what they are promising to actually implement in the coming weeks, months and years?"
He said that there was "still a lot of criticism" of the latest proposals from Athens.
Dijsselbloem added that he expected discussions to be “difficult”.
With Greece running out of money, and facing a July 20 demand for a three billion euro (£2.16 billion) payment to the European Central Bank, a series of meetings this weekend could hold the key to the country's economic future
Saturday’s meeting of single currency countries’s finance ministers will be followed by a summit of Europe's leaders from all 28 members, including British Prime Minister David Cameron on Sunday.
Greek MPs have backed proposals for economic reforms in the hope of ending the country's debt crisis.
Punishing tax rises and spending cuts are being offered in return for a financial lifeline of 53.5 billion euro (£38.5 billion) to prop up the country's failing banking system and avoid the possibility of crashing out of the single currency.
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The country’s prime minister Alexis Tsipras acknowledged that the measures were a long way from the anti-austerity platform his radical Syriza party was elected on.
Urging the MPs to back his negotiating position, Mr Tsipras admitted he had made mistakes during his tenure and described the struggle with the creditors - the European Commission, European Central Bank (ECB) and International Monetary Fund (IMF) - as a battle.
"Now I have the feeling we've reached the demarcation line.
“From here on there is a minefield."