Like boxers who heard the bell, like rhinos during the mating season, that's what the sparring between Barack Obama and Benjamin Netanyahu has come to resemble. Adrenalin pumping in the veins, eyes seeing red, and in their ears the cries of their supporters: "Knock his teeth out," "Let him have it," "Where's the blood?" The only thing missing is good sense.

Since the days they took office, the prime minister and the U.S. president have behaved like heroes in a Greek tragedy, bound by fate and waiting for the inevitable confrontation. Netanyahu saw in Obama and his aides a group of leftists who want to overthrow him and bring about "regime change" in Israel. Obama saw in Netanyahu a liar and subversive who is rallying the support of the Jewish lobby to foil U.S. foreign policy in the Middle East. The only surprise was that the two have managed to restrain themselves for a year before the exchange of diplomatic blows.

Now they are fighting over honor. "We are not willing to be suckers," was how Netanyahu once summed up his political worldview. "Insult," "humiliation," is what senior administration officials cried after Israel announced that 1,600 new housing units would be put up in Ramat Shlomo - a declaration made during Vice President Joe Biden's visit to Israel. On both sides they are talking in terms of life and death: Netanyahu's backers charge Obama with sentencing Israel to death via the Iranian nuclear program and "Auschwitz borders" from which rockets would be fired onto Tel Aviv and Ben-Gurion International Airport. For their part, the Americans warn that Israel's desire for settlements is endangering their soldiers in Afghanistan and Iraq.

The cheerleading only encourages the rivals not to give in. Obama was congratulated by The New York Times for his firm stance against Bibi and the settlements. Finally he has shown that he's a man, he was told. The right in Israel has called on Netanyahu to stand tall for the nation and throw the two-state solution into the garbage once and for all, making clear to the evil Americans that Israel will put a million Jewish settlers in the settlements. That is why you were elected, he is being reminded, not to surrender to Hussein Obama. Netanyahu agreed, went back to his ideological hearth and declared that construction in East Jerusalem will continue and settlement expansion in the West Bank will resume in the summer.

It's too bad that Netanyahu and Obama didn't stop and think about the implications of their actions. Let's assume Netanyahu overcomes American pressure and steps up construction in the territories. He will be applauded on the right and his rule will be secure for another two years, or maybe three, with the given coalition, but how would this folly serve Israel's national interest? It would only lead to deepened international isolation, foil a settlement with the Palestinians and waste billions.

Obama's gamble is even more risky. The Americans assume that the minute he stops to take a breath, Netanyahu will recall Israel's great dependence on the United States and give in to the ultimatum, as in past crises. Even the fabled David Ben-Gurion, who declared the existence of Israel's third kingdom at the end of the Sinai Campaign in 1956, caved in two days later and agreed to withdraw from the peninsula. The combined threat of Dwight Eisenhower and the Soviet leaders was enough to reverse Ben-Gurion's promise that "we will not stand idly by when we are under attack - especially when the attack is unjustified."

Netanyahu is not Ben-Gurion. He has a weaker personality and his rule depends on Eli Yishai and Avigdor Lieberman, who are extremists. But herein lies the danger of isolating Israel: Netanyahu may brace himself behind his existential fears, assume that Obama has come to terms with the Iranian bomb and send the air force on a preemptive strike on Iran. If the United States kicks Israel, we can ignore their calls not to hit Natanz. Thus a relatively minor dispute over the construction of a new neighborhood in Jerusalem may ignite a regional war.

The severity of the danger requires that this crisis be contained quickly. Someone needs to tell Obama not to push Israel into a corner and to remind Netanyahu what the true balance of power is. The Americans may be polite, and it's not nice that they remembered to oppose Israeli construction in East Jerusalem after they turned a blind eye for 42 years. But the American rhino is bigger and more powerful, and if he really becomes angry, the shock of his blow may be too painful to bear.