Israeli Prime Minister Benjamin Netanyahu on Sunday called on world governments to waste no time in stopping "Iran's race to arm itself with a nuclear weapon."

He was speaking to ministers and the media before a closed-door briefing to his cabinet on a report from the UN's atomic watchdog, which said it had "serious concerns regarding possible military dimensions" to Iran's nuclear programme.

Netanyahu said that the International Atomic Energy Agency's report "confirms the allegations of many countries in the world, Israel among them, that Iran is systematically developing nuclear weapons."

"Every responsible government in the world must draw the obvious conclusions," he added. "The international community must, in a timely manner, halt Iran's race to arm itself with a nuclear weapon, a race that endangers the peace of the entire world."

Israel, which has the Middle East's sole if undeclared nuclear arsenal, has long accused Iran of trying to develop atomic weapons under cover of a civilian nuclear programme.

Tehran denies that charge and has accused Israel of trying to sabotage its civilian nuclear programme and kill its nuclear scientists.

Israeli media in recent weeks have been full of chatter suggesting a pre-emptive strike on Iran's nuclear facilities was being seriously considered by Netanyahu and Defence Minister Ehud Barak.

The speculation came as the IAEA released its report last week, saying it had "credible" information that Tehran "has carried out activities relevant to the development of a nuclear explosive device."

Israeli media commentators have suggested that the severity of the report could bring increased international pressure on Iran and thereby lessen the near-term likelihood of an Israeli strike.

US President Barack Obama has called for new sanctions and isolation for Iran over its nuclear programme, but Russia and China, which as permanent members of the UN Security Council could veto such measures, have so far responded coolly.

On Sunday, Israeli newspaper Yediot Aharonot reported that French President Nicolas Sarkozy had pledged support for strong sanctions against Iran in a letter that came after the French leader was reported to have called Netanyahu a "liar."

The Elysee Palace confirmed that a letter had been sent to Netanyahu, but gave no detail on what Yediot said was an unusually warm, handwritten letter signed "with friendship," in an apparent bid to smooth over the diplomatic flap.

Sarkozy was reported to have called Netanyahu a "liar" in comments to US Obama that were inadvertently transmitted over a system used for translation at the G20 summit in Cannes, a French media website reported.