Several thousand leftists have rallied in Paris to "give Greece a chance" two days ahead of a critical summit of eurozone leaders on a bailout.

For Communist Party leader Pierre Laurent, "it's about knowing whether the democratic choice of a people ... is the guiding law or (if it's) the rule of austerity of the financial markets that governs the people."

Greece's new radical leftist government is in a stand-off with international creditors to reach a loan deal to avoid defaulting on debt payments at the end of the month, threatening an exit from the 19-nation eurozone.

Far-left political activist Clementine Autain said that Europe is faced with a "humanitarian emergency" brought on by "neo-liberal political choices" that have failed to reduce Greece's debt.