The EU, IMF and European Central Bank have made further spending cuts, labour market reforms and bank rescues a condition of extending a new bailout.
European Commission Vice President Neelie Kroes told a Dutch newspaper that there would be "absolutely no man overboard" if Greece left the euro.
Greek party leaders are meeting on Tuesday amid a general strike.
A previous meeting on Sunday night proved inconclusive, leading to further last-minute talks between Prime Minister Lukas Papademos and the troika of official lenders on Monday.
The leader of the left-wing Syriza party coalition, Alexis Tsipras, repeated a call on Tuesday either for Greece's debts to be written off, or else for the country to pause its debt repayments for three years.
Meanwhile, public transport and the country's ports ground to a halt as two of the largest Greek public-sector unions began a strike on Tuesday in protest at continuing austerity.