"Today we quite simply have to let the Greek people express themselves," Sapin told iTélé TV, judging it "normal" that they be allowed to do so.
But, he went on, "you can't reach and agreement with someone who says no."
On Wednesday Hollande called for an "immediate agreement", appearing to contradict Merkel's declaration that no deal could be reached before the referendum.
"I want us to reach an agreement according to European rules," he said during a visit to the French city of Lyon. "It should be reached before the referendum, it wouldn't make much sense after the consultation."
In contrast to Merkel's pugnacious stance, Hollande said that France "is not for vetoes, not for brutality".
The Socialist speaker of the National Assembly, Claude Bartolone, also criticised the Germans for refusing to negotiate.
"Europe without Greece would not really be Europe any more," he told France Info radio.
Although Sapin seemed to have given up on the prospect of a deal before Sunday, he, too, said that France had hoped for a deal on Wednesday.
"We have a capacity for dialogue with Greece that Germany doesn't have for historical reasons," he commented.
Athens has called for the repayment of loans imposed on Greece by Germany during its occupation of the country during World War II, which is still remembered with bitterness by many Greeks.
Eurozone finance ministers agreed Wednesday to wait until after the referendum before holding any more talks, saying there were "no grounds" for further discussion.