Speaking during her visit to Moscow, Tzipi Livni said that now that Russia has started nuclear fuel deliveries to the Iranian nuclear power plant in Bushehr, any further uranium enrichment could serve a military purpose.
She said Iran's neighbors realize that a nuclear Iran would pose a colossal threat, and urged tougher sanctions against the Islamic Republic.
Sanctions applied so far against Iran have had only a limited effect, she said.
The minister also warned that the lack of a tough response from the international community to Iran's uranium enrichment program could set a dangerous precedent in the Middle East.
Israeli accusations that Iran is developing nuclear weapons come despite a generally positive report on Tehran's compliance with the non-proliferation regime by the UN nuclear watchdog and a U.S. intelligence report saying Iran had halted its nuclear weapons program in 2003. Both reports were published late last year.
Iran, which possesses long-range missiles that can be armed with nuclear warheads, refuses to recognize the right of Israel to exist as a nation state, and repeated anti-Israeli statements by President Mahmoud Ahmadinejad have added fuel to the fire.
"I believe Russia and the international community understand, as Israel does, that Iran's possession of nuclear weapons must be prevented. We must thwart this in the UN Security Council by applying more effective sanctions," Livni said on Wednesday.
Iran's top nuclear negotiator arrived in Beijing earlier on Thursday as his country sought to persuade China to resist new UN sanctions against Tehran over its nuclear program.
During his two-day visit, Saeed Jalili, secretary of Iran's Supreme National Security Council, will meet with Chinese Foreign Minister Yang Jiechi and other high-ranking officials to discuss bilateral relations and the Iranian nuclear issue.
"Certain countries have used various pretexts and made groundless accusations in a drive to transfer Iran's 'nuclear case' to the UN Security Council. But today the inconsistency of their accusations has become clear from their own reports," Jalili said in an interview with Iranian television on arriving in the Chinese capital.
He confirmed Tehran's readiness to continue cooperation with the United Nations nuclear watchdog, the International Atomic Energy Agency, and to honor its international commitments.
Jalili's visit to Beijing comes days before a planned meeting of foreign ministers from the five permanent members of the U.N. Security Council plus Germany in Berlin next Tuesday to discuss possible new sanctions against Iran.
Two sets of UN Security Council sanctions are currently in place against Tehran over its refusal to halt uranium enrichment, which can be used in both electricity generation and weapons production. A further round of more stringent sanctions has so far been blocked by China and Russia.
Iran insists that it needs nuclear energy for electricity generation and not for weapons production, and has pledged to clear up all remaining questions over its nuclear program by late February.