This is the big embarrassing question that Muhammad al-Baradai, director-general of the International Atomic Energy Agency (IAEA), has been struggling to avoid.
Whenever he is pressed to explain the apparent double standard, al-Baradai chooses to equivocate - a response that many see as an indirect admission of the IAEA's inability to confront Israel over its alleged huge stockpile of nuclear, chemical and biological weapons.
Al-Baradai arrived in Israel on Tuesday as an invited guest in what was described as a "routine visit". He told reporters in Tel Aviv that he would like to see Israel support the Nuclear Non-proliferation Treaty as well as sign an additional agreement committing it to disclose information on any potential nuclear-related exports.
The stated principal objective of al-Baradai's visit is to sell the concept of the Middle East as a nuclear-free zone.
But, according to many experts, an almost equally important objective is to counter the accusation often levelled by Arab and Muslim countries - that the IAEA is a pliant instrument of US foreign policy.
Policy of ambiguity
Israel says it accepts "in principle" the concept of a nuclear-free Middle East. At the same time, it insists that its sizable nuclear arsenal shouldn't be the subject of international scrutiny until comprehensive peace is achieved throughout the Middle East.
Accordingly, Israel has consistently refused to admit officially that it possesses nuclear weapons. Instead, successive governments have adopted a policy which states that "Israel will not be the first country to introduce nuclear weapons to the Middle East".
Israel's prickliness on the issue is best illustrated by the case of Mordechai Vanunu, the nuclear technician who was kidnapped, tried and imprisoned in 1986 for blowing the whistle to a UK newspaper on Israel's atomic reactor outside Dimona in the Negev Desert.
The once-secret atomic reactor
outside Dimona in Negev Desert
This decades-old rigid policy of nuclear ambiguity is, however, considered unconvincing and anachronistic by a large section of the international community, and by the Arab world as sheer deception.
"We know, Israel knows, and the world knows that Israel possesses nuclear weapons. We also know that Israel quibbles and equivocates about this," said Muhammad Qadri Said, a scholar at al-Ahram Centre for Strategic Studies in Cairo, Egypt, in an interview to Aljazeera.net.
Said said neighbouring Arab and Muslim countries might be forced to "draw the necessary conclusions" if Israel continues to insist on threatening the Middle East with its nuclear weapons.
"If the international community fails to deal with the Israeli nuclear arsenal, then countries such as Egypt might rethink its present way of thinking.
"There are several scenarios. Some countries could enter into an alliance with nuclear powers, others might resort to increasing their conventional forces," Said said.
Israeli leaders and officials routinely say the nuclear arsenal is a defence of last resort against possible annihilation of their state. But many Arabs dismiss this argument as "only a pretext", and say Israel is more than capable of defending itself with conventional weapons.
In any case, they add, the decades-old strategic alliance between Israel and the US grants the Jewish state not only security but a qualitative edge over all the Arab countries combined.
"If the international community fails to deal with the Israeli nuclear arsenal, then countries such as Egypt might rethink its present way
Muhammad Qadri Said,
al-Ahram Centre for Strategic Studies, Cairo
Some Arab experts also express concern about the likelihood of Israel becoming a very dangerous state if Jewish fundamentalists, who are now threatening to topple the government of Ariel Sharon for his Gaza withdrawal plan, ever grab political power.
Indeed, Jewish fundamentalist leaders - the former tourism minister Benny Elon of the quasi-fascist National Union party, for one - have been reported as saying during a meeting with American evangelical leaders that "Jews and Christians ought to launch a worldwide crusade for the purpose of wiping out Islam".
Moreover, most of the messianic Jews, such as the Gush Emunim movement, are deeply steeped in the theological doctrine that the "redeemer" or Jewish Messiah wouldn't appear unless there is a genocidal event and bloodshed on a very large scale.
According to some Israeli intellectuals, the country might become a serious threat to its neighbours if Jewish extremists one day get their hands on Israel's nuclear weapons.
Such concerns notwithstanding, Israeli officials and strategic experts insist that Iran, not Israel, is the "real threat".
Speaking to Aljazeera.net, Ephraim Inbar, a fellow at the Begin-Sadat Centre for Strategic Studies at the Bar Ilan University, Tel Aviv, said Iran is dangerous because of its "revolutionary government and because of its threats against Israel".
Mordechai Vanunu was jailed for
18 years for spilling N-secrets
"Israel doesn't pose a threat to Iran, but Iran poses a threat to Israel," he said.
Asked to explain why Iran and other countries in the region should meekly continue to live in the shadow of Israel's nuclear arsenal, Inbar avoided giving a direct answer.
Israel, he said instead, would be willing to "discuss the nuclear issue" when a "comprehensive and stable peace" is reached.
But when Israeli officials and strategic experts talk of "comprehensive peace", what they leave unsaid is that this peace would have to be on Israeli terms.
To the region's Arabs and Muslims, that would be tantamount to assertion of Israeli supremacy and hegemony over a vast region extending from the Indian subcontinent to the Atlantic Ocean.
Better or worse?
Inbar and al-Ahram Centre's Said differ sharply on whether the possible appearance of a second nuclear-armed state in the Middle East, such as Iran, would bring about stability or exacerbate tensions.
Said argues that the Mutual Assured Destruction (MAD) theory, which many scholars now believe kept the peace between the former Soviet Union and the West during the cold war, could also work in the Middle East.
"Israel doesn't pose a threat to Iran, but Iran poses a threat to Israel"
Begin-Sadat Centre for Strategic Studies, Bar Ilan University,
He cites the example of India and Pakistan - two avowed nuclear enemies that have now been forced to normalise their relations and seek a more peaceful coexistence.
On the other hand, Inbar says it is doubtful whether MAD would work effectively in the Middle East given the "fragile and unstable regimes in the area".
Furthermore, he says, the Soviet Union and the US had a early-warning span of more than 20 minutes while in the Middle East it's only a few minutes.
"Due to the relatively short distances, the chances for miscalculation here are greater than it was between the Soviet Union and the United States," Inbar says.
Soon there may be more cause for Arab concern, however.
Israel is believed to be developing a fleet of nuclear-armed submarines capable of striking at distant shores of Arab and Muslim countries.
When deployed, the submarines would supplement its existing land-based nuclear weapons, along with their complete delivery systems, such as the Yarihoo long-range missiles as well as a large squadron of long-range, state-of-the-art fighter aircraft such as the F-15-I supplied by the US.
Nuclear-armed Israeli subs could
some day strike distant shores
Reports recently spoke of Israel fitting a number of modern submarines gifted by Germany with nuclear warheads.
Israeli officials, in keeping with the country's nuclear-ambiguity policy, have refused to confirm or deny the reports. But what is beyond doubt is that Israel, using its special relations with the US, is determined to maintain its nuclear monopoly and military supremacy in the Middle East.
Indeed, many Arab experts are convinced that the overthrow of Saddam Hussein was a part of the same grand design to perpetuate Israel's military dominance in the region - a suspicion backed by retired US general Anthony Zinni's recent disclosures.
For similar reasons, they say, Israel is inciting the international community, notably the US, to crack the whip on Iran, a regional power with nuclear ambitions, even as it refuses to come clean on its own huge nuclear arsenal.
"I have no power to pressure Israel"
International Atomic Energy Agency
In all likelihood, al-Baradai understands the irony of the situation better than anybody else. But, then, he surely has no illusions about the limits of his ability to confront Israel in view of the US connection. He almost admitted as much when he said in Tel Aviv this week: "I have no power to pressure Israel."
Which partly explains why Israel but not its Arab and Muslim neighbours can get away with building and stockpiling WMDs.