The furor over the second settlement freeze should not obscure the divergence between Prime Minister Netanyahu and the Obama administration over the Iranian nuclear program. In Washington last week, Netanyahu argued that Iran's march to the bomb cannot be averted by porous economic sanctions; Secretary of Defense Robert Gates replied by reiterating his faith in the sanctions regime.

If this divergence is not bridged, Israel will have to weigh unilateral action, though this option too is currently blocked by the Obama administration. Ostensibly the rationale for the president's position is the desire to give sanctions a chance. However, it may equally reflect a sense of resignation that a nuclear Iran is the lesser evil, and the belief that the nuclear stability that governed U.S.-Soviet relations during the Cold War could be replicated in the Israeli-Iranian context.

A good example is Bruce Riedel's article in the September-October issue of The National Interest ("If Israel Attacks" ), where he argues that the repercussions of an Israeli attack would be so severe that Israel should be dissuaded from it. As compensation, the U.S. should provide Israel with sweeteners that will allow it to live with the Iranian bomb. These inducements, in order of ascending desirability, would be: NATO membership, a U.S. nuclear umbrella, and support for an Israeli second-strike capacity.

Riedel is intellectually honest enough to admit that NATO has no allure for Israel even under the dubious assumption that it would be offered membership. NATO decisions must be made unanimously, and Turkey's membership vitiates any effective intervention by the organization on Israel's behalf. The United States learned the unanimity lesson itself when George W. Bush was forced to form the "coalition of the willing" to depose Saddam Hussein, and was faced with opposition by Gerhard Schroeder and Jacques Chirac in NATO. In any event, austerity policies in Europe are hollowing out the continent's military forces to the extent that they will soon only be able to mount expeditionary-force activities, and this will be too little and too late for Israel.

The next palliative is an American nuclear umbrella. This sounds reassuring until one recalls what Henry Kissinger called the "troubled partnership" back in the 1960s, when Charles de Gaulle voiced his reluctance to rely on the American nuclear deterrent, and his preference for an independent French force de frappe (strike force ). Once the Soviets acquired delivery systems that could pose a threat to the American heartland, reasoned De Gaulle, the U.S. would not risk the nuclear devastation of its cities to defend France against a Soviet attack. To allay these concerns, the U.S. sought to provide assurances by maintaining substantial forces in Europe as trip wires and hostages to a Soviet attack, thus guaranteeing an American riposte.

Iran is not content with the bomb, but is building a delivery system to go with it. If Riedel fears the repercussions of attacking Iran now, wait till the Islamic Republic has the capacity to retaliate against European and American population centers. It is doubtful that the United States will provide Israel with the same trip wires that it provided the Europeans in terms of stationing sizable contingents of American forces in Israel, particularly at a time of retrenchment.

This brings us to Riedel's extremely optimistic piece de resistance: U.S. support for a durable and credible Israeli second-strike capacity, including even nuclear submarines and state-of-the-art attack planes. Here the only precedent is U.S. assistance to Great Britain in maintaining a nuclear submarine force following the scrapping of Britain's Skybolt missile system in the 1960s.

Such a development raises obvious problems. Such an arrangement, to be effective, must be overt, and puts paid to Israel's policy of nuclear ambiguity. This is consistent with Riedel's view as expressed in these pages, when he warmly reviewed Avner Cohen's book "The Worst-Kept Secret," which advocates scrapping such ambiguity. It means that the United States must have Jerusalem's back in repelling international attempts to denuclearize Israel. Once Israel could have confidence that such support was a given. But when Israel must pay in diplomatic and perhaps territorial coin to get the U.S. to quash Goldstone (with the report's repercussions for criminalizing American actions ) and the furor over the Turkish flotilla, Israel may also be called upon to make future concessions to retain American support for its nuclear deterrent.

It is equally difficult to see Israel as the singular beneficiary of such a policy. Having blessed and contributed to an independent Israeli deterrent, how will the United States be able to refuse the Saudis and the Egyptians when they demand similar consideration? Israel has a long experience of American promises to maintain its qualitative edge, only to see similar state-of-the-art hardware being funneled to the Gulf in more impressive quantities.

Even assuming that these and other difficulties could be overcome - a most questionable assumption - the analogy between Iran-Israel and U.S.-USSR is faulty. There are many reasons for this, but let us suffice with one: The escalation ladder is much shorter. Israel and Iran will not engage in proxy wars on the Korean Peninsula, the Horn of Africa or Indochina. Even if Iran merely relies on its proxies in Gaza and Lebanon, the effects will be felt in Israeli cities and in the civilian rear, abbreviating the path to the nuclear threshold. If Israel has the capacity to eliminate or even retard the threat of a nuclear Iran, it should act now rather than rely on promises that may prove hollow or unsustainable.

Dr. Amiel Ungar, a political scientist, is a regular contributor to Haaretz English Edition.