While the internal political maneuverings and party primaries have filled the news pages, the main challenges to the new Israeli leadership under Ehud Olmert are more likely to come from outside. In addition to renewed Palestinian terror, the potential for a Hamas takeover of what remains of the Palestinian Authority and another Hizbullah attack from Lebanon, the agenda includes the need to respond effectively to Iran's nuclear program as Teheran nears the "red line." Under Prime Minister Ariel Sharon Israel continued the earlier policy based on an international approach, recognizing that the threat from Iranian doomsday weapons is not limited to Israel but covers Europe, the Arab Middle East and the United States. Unilateral Israeli action would be costly and perhaps unnecessary, unlike the case in 1981, when the US and Europe ignored the dangers posed by Saddam Hussein's efforts to put his finger on the nuclear trigger. The hope was that the world's leaders had learned to take such threats more seriously and act in concert and in a timely manner. But the "international community" moved very slowly, hoping the problem would disappear, either through regime change led by reformers in Iran or via diplomacy and negotiations, as if Teheran was part of postwar and post-nationalist Europe. Iran's leaders used the time effectively, moving closer to the threshold that would give the radical Islamic regime nuclear weapons and long-range missiles to send to targets across the globe while avoiding isolation. Suddenly, the rest of the world woke up to the dangers as Iran resumed operations of its uranium-enrichment facilities to provide the fissile material for making weapons. After delaying for more than a year, the International Atomic Energy Agency has finally acknowledged the plain evidence and declared Iran to be in non-compliance regarding its commitments under the Non-Proliferation Treaty. Hopes that the Iranian leadership was planning to trade its nuclear assets for recognition by Washington in some sort of grand bargain have disappeared without a trace or shred of evidence. Belatedly, Europe and Russia have recognized the hollowness of earlier claims that Iran's nuclear program did not pose a threat, and that diplomacy alone could prevent Teheran from crossing the threshold. But pious hopes and fervent beliefs in peace are poor substitutes for realistic policies. Like the players in a Greek tragedy the members of the "international community" may be doomed to doing little more than witnessing the very unhappy ending. IN THIS situation, some diplomats have suggested that Israel rely on mutual deterrence for security, based on the Cold War analogy. This was always a difficult proposition, even while the previous Iranian government provided a fa ade of moderation and gradual political evolution toward tolerance and rationality. But this thin hope has disappeared in the wake of President Mahmoud Ahmedinajad's genocidal threats and Iran's continued support for Hizbullah and various Palestinian terror organizations. Iran's religious leaders remain totally isolated, unable to detect when they are edging close to the brink of mutual destruction, or to manage a nuclear crisis. So what is to be done? The 1981 Begin Doctrine is often cited in such discussions, but the differences between then and now are greater than the similarities. While scenarios based on a massive three-week air operation involving hundreds of sorties against dozens of targets are overdone, it would take more than one bombing run to set back Iran's nuclear program for at least a decade and prevent serious retaliation. As a result, a preventive strike remains the last resort option, if all other efforts have failed. Policies based on last-resort options are also predicated on the assumption that it is possible to know when the time for this approach has been reached. But even the best intelligence services can provide only educated guesses. If just a few months remain to prevent completion of this nuclear program, the choices narrow, while a longer period - three years of more, according to some views - still provides time for sanctions, isolation of Iran and concerted international action. A UN Security resolution approved by Europe, Russia and China, with substantive measures to isolate Iran in areas such as sports, might send enough of a jolt to force some recalculation on the part of the Iranians, even at this late date. Although the odds of sanctions having a significant impact are small, the risk of trying this approach for a few more months is probably justified. And if this approach fails to change Iranian policy, the precedent for international action will have been set. It's still a long shot, by any standard, but it's the only option short of unilateral military action.