If Iran managed to obtain a nuclear weapon it would be "a threat to Israel, the region and the world," he said. "It is my duty to prevent a new holocaust."
Speaking at the beginning of a three-day visit to the Middle East. Hollande said Jewish history teaches that threats of destruction must be taken very seriously.
"France will not yield on nuclear proliferation," Hollande told Israeli Prime Minister Benjamin Netanyahu.
Hollande spoke ahead of a new round of talks in Geneva next week involving Iran, the five UN veto powers and Germany, who have been negotiating over temporarily curbing Tehran`s nuclear programme in return for a lifting of sanctions.
Netanyahu charged that the deal being negotiated was "bad" because it allows Iran the capacity to produce the materials needed to make a bomb within 26 days.
Israel could live with a deal that would see Iran at least "take some steps" toward dismantling uranium centrifuges and plutonium reactors, he said.
But he said he was "very concerned" that the deal being negotiated would settle for less, and ease "with one stroke of the pen sanctions that took years to put in place."
The Israeli prime minister has long sounded the alarm bells over Iran`s atomic activities and is set to once again press his case when he meets Russian President Vladimir Putin in Moscow on Wednesday and US Secretary of State John Kerry in Jerusalem on Friday - his second visit to Israel in 10 days.
"I hope that we will succeed in convincing our friends this week, and the days after, to reach a much better deal," he told his cabinet earlier Sunday.
President Shimon Peres, on receiving his French counterpart in Jerusalem, said Israel "appreciates" France`s "steadfast" and "determined" stance in the Geneva talks.
"We will never permit Iran to have nuclear weapons," Hollande told Peres.
"So we seek an agreement. We want an agreement. Because we think that negotiations, diplomacy is preferable ... but that agreement - which can be reached - will not be possible unless Iran gives up nuclear weapons." Hollande`s visit to Israel was to include a stop-over in the West Bank. He is to spend Monday morning in nearby Ramallah, where he will meet with Palestinian President Mahmoud Abbas. He is set to address Israel`s Knesset, or parliament, back in Jerusalem in the afternoon.
On Tuesday, he is scheduled to visit the graves of the victims of a March 2012 terrorist attack on a French Jewish school.
The attack by Islamist gunman Mohamed Merah in Toulouse was the worst assault on Jews in France in 30 years, and led to a tightening of anti-terrorism legislation.
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