In a visit to Paris, Netanyahu praised French pressure on Iran and called for "even tougher sanctions" than the ones currently in place.
"The sanctions are taking a bite out of Iran's economy ... unfortunately they have not stopped the Iranian program," he said.
Israel has been an outspoken critic of Iran's disputed nuclear program, repeatedly saying that Tehran is well on the way to developing an atomic bomb. Israel believes a nuclear-armed Iran would pose a threat to its very existence, citing Iranian leaders' frequent calls for destruction of the Jewish state, Iran's development of long-range missiles and Iranian support for Arab militant groups.
"Given the history of the Jewish people, I would not sit by and write off a threat by those who say they are going to annihilate us," Netanyahu told reporters. He said Arab nations, too, would be "relieved" if Iran were militarily prevented from obtaining nuclear arms.
Tehran has long insisted it is not developing atomic weapons. But French President Francois Hollande said Wednesday that Iran has not proven that its nuclear program is aimed only at civilian use.
Hollande has supported a push for tougher European Union sanctions on Iran, but he also wants to keep the door open to dialogue, and has opposed Netanyahu's talk of possible military action.
"It's a threat that cannot be accepted by France," Hollande said at Netanyahu's side, warning that a nuclear-armed Iran would be a danger to the region and the world.
France, Hollande said, "is ready to vote for other sanctions, as many as necessary."
"We must make sure that through pressure, sanctions and later through negotiations, Iran renounces its intention to have access to nuclear weapons. I am working in that spirit," he said.
Israel has repeatedly threatened to attack Iran if it concludes that international sanctions and diplomacy are failing to halt the nuclear program. In a speech to the United Nations in September, Netanyahu suggested that the world had until next summer at the latest to act or it would be too late to prevent the Iranians from making a bomb.
In his comments Wednesday, Netanyahu said he hopes the issue will be resolved peacefully.
Netanyahu and Hollande also talked about the possibility of resuming Israeli-Palestinian peace negotiations in Paris.
"President Hollande can invite (Palestinian President Mahmoud) Abbas to the Elysee," the French presidential palace, Netanyahu said. "I'm here, I'm ready. ... The only way we can complete the negotiations is to begin them."
Hollande responded: "That's a good idea."
The two leaders disagreed, however, about other issues.
France has long opposed Jewish settlement building in the Israeli-occupied West Bank and east Jerusalem, and supports the creation of a Palestinian state. Netanyahu says he also supports the idea of Palestinian independence, but he has added so many conditions that the Palestinians do not take his offers seriously.
France also voted for Palestinian membership in UNESCO, the Paris-based U.N. cultural and educational body, a year ago. The Palestinian president is now moving forward with his plan to seek upgraded observer status at the U.N. in New York next month, despite American and Israeli threats of financial or diplomatic retaliation.
Netanyahu criticized Palestinian efforts toward international recognition before a peace deal is reached, saying that "going to the U.N. with unilateral declarations is not negotiations. It's the opposite of negotiations."
Netanyahu's visit is the first to France under Hollande, a Socialist seen as somewhat less Israel-friendly than his conservative predecessor Nicolas Sarkozy.
It's also Netanyahu's first visit since a radical Islamist gunman killed a rabbi and three Jewish schoolchildren in southern France in March, this country's worst terrorist attack and worst anti-Semitic attack in years.
Netanyahu travels Thursday to Toulouse to pay homage to the victims.
Netanyahu's visit was marked by demonstrations by both pro-Palestinian and pro-Israel activists. At one protest in front of Paris' Opera Garnier, about 200 supporters of the Palestinian cause waved banners and distributed leaflets calling for a boycott of Israel.
Youssef Berbero, a protester, called Netanyahu's visit "an insult to democracy and to the Palestinian people being massacred."