"I call on you to act now, before it is too late. Revoke Iran's membership in the United Nations," Lieberman said in a letter to the new UN chief obtained by AFP.

"Pressure the Security Council to impose the harshest and most extensive set of sanctions the world has ever seen, and halt Iran's progress towards nuclear weapons."

Israel, believed to be the sole nuclear power in the Middle East, claims, together with the United States, that Iran's nuclear programme is aimed at obtaining an atomic bomb despite Tehran's denials.

Iranian President Mahmoud Ahmadinejad's repeated calls to wipe Israel "off the map" have been a source for deep concern in Israel, which has vowed to do everything in its power to prevent the development of an Iranian nuclear bomb.

"The State of Israel can, and will, stand alone against Iran, but we should not be asked to. If (Iran is) allowed to achieve nuclear weapons, the entire free world will pay a heavy price -- Israel will be the first, and will pay the heaviest price," Lieberman wrote.

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