General Dagan, head of the Mossad, the Israeli intelligence agency, made the comments in an address to parliament's foreign affairs and defence commission, according to military radio.

"If Iran's nuclear programme continues at its current pace, they will succeed in having a bomb within three of four years," Dagan was quoted as telling the commission.

The general had in November 2003 told the same commission that Iran's nuclear programme constituted "the greatest threat" to Israel since its creation in 1948.

Prime Minister Ehud Olmert has on a number of occasions said Israel will "not tolerate" an Iran with nuclear weapons capability.

A week ago, Olmert appeared to admit -- in breach of the Jewish state's decades-long policy of ambiguity -- that Israel possessed nuclear weapons.

The blunder sparked outrage, with lawmakers from across the political spectrum calling on the premier to resign.

Iran, meanwhile, is facing United Nations sanctions for refusing to stop enriching uranium, which the West fears may be used for weapons development but which Tehran insists is destined for its civilian energy programme.

But the Security Council's five veto-wielding members -- Britain, China, France, Russia and the United States -- plus Germany have been struggling to reach consensus on a resolution because of Russia and China's opposition to harsh sanctions favored by Western states.

Israel is particularly fearful of Tehran developing a nuclear bomb in the light of President Mahmoud Ahmadinejad's constant threats against the Jewish state and his calls for its to be "wiped off the map".

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