Athens had not by late Sunday delivered a response to the latest proposal presented by lenders in Brussels.
It was not certain as a result when representatives of the country’s international creditors would return to Athens for resumption of bailout talks.
In a five-hour meeting Friday, lenders proposed fresh cuts representing 2 percent of GDP, or a further 3.6 billion euros in austerity measures.
In a speech before SYRIZA’s central committee on Saturday, Tsipras lashed out at Greece’s creditors, calling on them to revise their “irrational demands” of Greece.
“We will not agree to demands that are not backed up by logic and numbers,” he said.