Jews worry for a living; their tragic history compels them to do so. In the next few years, there will be plenty to worry about, particularly when it comes to Israel. The current operation in Gaza won't do much to ease these worries or to address Israel's longer-term security needs. The potential for a nuclear Iran, combined with the growing accuracy and lethality of Hamas and Hizbullah rockets, will create tremendous concern. Anxiety may also be provoked by something else: an Obama administration determined to repair America's image and credibility and to reach a deal in the Middle East.

Don't get me wrong. Barack Obama—as every other U.S. president before him—will protect the special relationship with Israel. But the days of America's exclusive ties to Israel may be coming to an end. Despite efforts to sound reassuring during the campaign, the new administration will have to be tough, much tougher than either Bill Clinton or George W. Bush were, if it's serious about Arab-Israeli peacemaking.

The departure point for a viable peace deal—either with Syria or the Palestinians—must not be based purely on what the political traffic in Israel will bear, but on the requirements of all sides. The new president seems tougher and more focused than his predecessors; he's unlikely to become enthralled by either of Israel's two leading candidates for prime minister—centrist Foreign Minister Tzipi Livni, or Likudnik Benjamin Netanyahu. Indeed, if it's the latter, he may well find himself (like Clinton) privately frustrated with Netanyahu's tough policies. Unlike Clinton, if Israeli behavior crosses the line, he should allow those frustrations to surface publicly in the service of American national interests.

The issue at hand is to find the right balance in America's ties with Israel. Driven by shared values and based on America's 60-year commitment to Israel's security and well-being, the special relationship is rock solid. But for the past 16 years, the United States has allowed that special bond to become exclusive in ways that undermine America's, and Israel's, national interests.

If Obama is serious about peacemaking he'll have to adjust that balance in two ways. First, whatever the transgressions of the Palestinians (and there are many, including terror, violence and incitement), he'll also have to deal with Israel's behavior on the ground. The Gaza crisis is a case in point. Israel has every reason to defend itself against Hamas. But does it make sense for America to support its policy of punishing Hamas by making life unbearable for 1.5 million Gazans by denying aid and economic development? The answer is no.

Then there's the settlements issue. In 25 years of working on this issue for six secretaries of state, I can't recall one meeting where we had a serious discussion with an Israeli prime minister about the damage that settlement activity—including land confiscation, bypass roads and housing demolitions—does to the peacemaking process. There is a need to impose some accountability. And this can only come from the president. But Obama should make it clear that America will not lend its auspices to a peacemaking process in which the actions of either side willfully undermine the chances of an agreement America is trying to broker. No process at all would be better than a dishonest one that hurts America's credibility.

Second, Obama will have to maintain his independence and tactical flexibility to play the mediator's role. This means not road testing everything with Israel first before previewing it to the other side, a practice we followed scrupulously during the Clinton and Bush 43 years. America must also not agree to every idea proposed by an Israeli prime minister. Our willingness to go along with Ehud Barak's make-or-break strategy at the Camp David summit proved very costly where more disciplined critical thinking on our part might have helped preempt the catastrophe that followed. Coordinating with Israel on matters relating to its security is one thing. Giving Israel a veto over American negotiating tactics and positions, particularly when it comes to bridging gaps between the two sides, is quite another.

If the new president adjusts his thinking when it comes to Israel, and is prepared to be tough with the Arabs as well, the next several years could be fascinating and productive ones. I hope so, because the national interest demands it. The process of American mediation will be excruciatingly painful for Arabs, Israelis and Americans. But if done right, with toughness and fairness, it could produce the first real opportunity for a peace deal in many years