"Our policy of ambiguity on nuclear arms has proved its worth, and it will continue," Sharon said on the eve of a meeting with Mohamed ElBaradei, director general of the International Atomic Energy Agency (IAEA).

Few people have been in any doubt that Israel has a nuclear capacity after the former technician Mordechai Vanunu blew the whistle in 1986 on the inner workings of the top-secret Dimona nuclear plant in the southern Negev desert.

Vanunu's punishment for spilling the beans to Britain's Sunday Times newspaper was an 18-year prison sentence for "espionage" that only ended in April.

However, Israeli authorities continue to cling to the 40-year-old mantra that the country "will not be the first to introduce nuclear arms in the Middle East".

Dimona, which was inaugurated in 1965, is one of two nuclear plants in Israel. A smaller research reactor is located at Nahal Sorek, south of Tel Aviv.

Under an understanding with the United States dating back to 1969, Israel has committed itself to abstain from any comment on its nuclear potential and not to carry out nuclear tests.

In return, the United States does not pressure Israel to adhere to the nuclear Non-Proliferation Treaty (NPT), which would oblige the Jewish state to submit its nuclear facilities to international supervision by the IAEA.

"This policy of ambiguity has effectively allowed Israel to acquire a deterrent force without incurring international sanctions," the Israeli nuclear analyst Reuven Pedatzur told AFP.

However Pedatzur said he believed the time had now come for Israel to lift the smokescreen in the wake of an increasing nuclear threat from the Islamic fundamentalist regime in Iran, which is now regarded as the Jewish state's number one enemy since the downfall of Iraqi leader Saddam Hussein.

"Faced with a country such as Iran which will soon have nuclear arms at its disposal and which has voiced its wish to destroy Israel, it will no longer be enough to leave vague threats hanging in the air as a deterrent."

The authorities' ability to maintain the smokescreen has been aided by censorship which leaves the media having to rely on the opinions of "foreign experts".

No Israeli leader has ever broken the long-standing taboo by unequivocally recognising the existence of a nuclear arsenal, but allusions have become less and less oblique.

The former premier Shimon Peres, considered the father of Israel's nuclear programme after reaching agreement with France back in 1956 for the provision of a nuclear reactor and uranium, effectively confirmed its existence in an interview with French television in 2001.

"The suspicion and the fog which surround this project are constructive, for it increases our power of deterrence," Peres, who was then foreign minister, said in a documentary on Dimona.

According to military historians, Israel came closest to utilising its tactical nuclear weapons during the 1973 Yom Kippur War in order to halt the advance of a column of Syrian tanks but the plans were called off when they suddenly retreated.

ElBaradei said in Moscow last week that Israel should "clarify" its nuclear activities and start working toward ridding the Middle East of nuclear weapons.

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