Eyebrows were raised in Jerusalem when, last month, US Assistant Secretary of State Rose Gottemoeller declared that "universal adherence to the NPT [the Nuclear Non-Proliferation Treaty] itself, including by India, Israel, Pakistan and North Korea... remains a fundamental objective of the United States." Washington's chief nuclear arms negotiator may have been reiterating official US policy, but what set off alarm bells among Israeli policymakers is the possibility that her comments might represent a shift in the long-standing US practice of avoiding any real pressure on Israel to sign and ratify the NPT. Israeli leaders are correct to be concerned about the possibility of such a policy shift. For nearly 50 years, the country has adhered to a policy of nuclear ambiguity, neither confirming nor denying foreign reports that its arsenal includes as many as 200 nuclear weapons. By joining the NPT, it would have to make a full disclosure about its nuclear program and commit itself to nuclear disarmament. (Only the five original nuclear weapon states - the US, France, Britain, China and Russia - are permitted to have nuclear arms.) Over the years, a number of attempts have been made by the international community to compel Israel to sign the NPT, which went into effect in 1970 and today has 189 signatories. In 1995, for example, the UN singled it out by passing a resolution calling for the establishment of a nuclear-weapon-free zone in the Middle East. The following year, Egypt and Syria unsuccessfully pressured president Bill Clinton to demand an Israeli signature on the treaty. Since then, additional attempts have been made to force its hand, largely in the context of the Iranian nuclear program. Most recently, in 2006, Syria promoted a Security Council resolution declaring the Middle East a nuclear-free zone and calling for sanctions against those countries that did not comply. BUT THE US has good reasons not to press Israel on this sensitive issue. First, any disclosure could induce a Middle East arms race just as the Iranian nuclear program threatens to do. Since 2006, more than a dozen countries in the region including Egypt, Turkey, Algeria and member countries of the Gulf Cooperation Council have been pursuing civilian nuclear energy, arguably as a hedge against developments in Iran. If Israel adopts an explicit nuclear doctrine, with or without joining the NPT, it may prompt these countries to develop nuclear programs even more quickly - virtually assuring that any non-proliferation goals of the Obama administration in the region are dead on arrival. Last year, the Arab League announced that Arab countries, all of which are signatories to the NPT, would walk away from it if Israel ever officially acknowledges it has nuclear weapons. Nor would full disclosure enhance deterrent power, as some policymakers and academics have argued. The suspicion alone remains a powerful deterrent force vis-Ã -vis its Arab neighbors. The policy of ambiguity has been a key factor in limiting Arab aggression - from Egypt's and Syria's limited aims in the 1973 Yom Kippur War to Saddam Hussein's decision to refrain from firing chemical warheads during the first Gulf War. Even some of the most ardent rejectionists no longer call for Israel's destruction, as is evidenced by the Arab peace initiative that Saudi Arabia began promoting in March 2002 and which has since been adopted by the Arab League. SHIMON PERES, the father of the nuclear program, was asked in 2000 if the time had come to finally acknowledge or deny nuclear capability. Peres relayed that when Amr Moussa, the then-foreign minister of Egypt, expressed an interest in seeing the nuclear research center near Dimona, he replied: "Amr, suppose I shall take you and you will see there is nothing there. You will be out of business and I will be out of business. It's better that you don't know - and I am not joking." Not only would joining the NPT likely spur a regional arms race - undermining the Obama administration's nuclear non-proliferation efforts - it could potentially destabilize the region at a time when the US must deal with the volatile situation in Iraq and, simultaneously, a belligerent Iran. Embryonic nuclear programs are less likely to have the control and operational safety features of the established nuclear powers. Moreover, new nuclear states are inherently dangerous because of their vulnerability to preemptive first strikes that could prompt them to launch their nuclear weapons in response to a real or perceived warning, thus increasing the risk for nuclear war. If any of the Arab countries currently pursuing civilian nuclear energy begin to develop nuclear weapons programs in response to disclosure (or the development of Iranian nukes), they would be particularly susceptible to these dangers. Under more favorable geopolitical circumstances, Israel may be persuaded to join the NPT and receive, in turn, a "nuclear umbrella" from the US. That President Barack Obama chose not to press Prime Minister Binyamin Netanyahu on this issue during their recent meeting at the White House, however, should not come as a surprise - despite his recent bold statements on the issues of nonproliferation and arms control. Perhaps in the wake of Gottemoeller's statement and subsequent deliberations, the Obama administration has come to understand that, at least for the time being, Israel's ambiguous nuclear policy, along with its refusal to join the NPT, is a force that promotes regional stability. The writer is a political consultant in Washington. This summer, he will be teaching a course on Israeli security and foreign policy at the University of Maryland.