Last night, rejecting criticism of his actions in Libya, President Obama outlined a standard for civilized multilateralism: “Sometimes, the course of history poses challenges that threaten our common humanity and common security,” he said. “Real leadership creates the conditions and coalitions for others to step up as well; to work with allies and partners ... to see that the principles of justice and human dignity are upheld by all.” If you should act, act where you can, and act together.

Obama gained a mandate from the U.N. Security Council, working with the European Union to rally the Arab League. He enlisted support from leaders of the Group of 20 in the process. His leadership, in short, did not just turn the tide against one Arab tyranny, but produced a model of statecraft for the region as a whole.

This model now has an even more important task. Obama should, and can, lead the Quartet (the U.S., U.N., E.U. and Russia) in presenting a new blueprint for Israeli-Palestinian peace. Whatever happens in Libya, America will never be seen as a champion of Arab democracy if it continues to appear cavalier about the occupation of the Palestinians.

The president made clear in his Cairo speech that Palestinian statehood is not simply an internal Israeli affair, nor is Israeli security the responsibility of the Israeli military alone. He knows that the chances of success in any bilateral talks between Israeli Prime Minister Benjamin Netanyahu and Palestinian Authority President Mahmoud Abbas are nil. He also knows what the product of good-faith negotiations must be.

From early in 2007 to September 2008, for example, Abbas and the former Israeli prime minister Ehud Olmert held 36 meetings. On the core issues, they wound up gravitating to virtually the same outline for a deal as produced in past negotiations at Taba and Geneva.

In late January, I interviewed both leaders and laid out what they had achieved in the New York Times Sunday Magazine: Their agreements in principle on security, land swaps based on the 1967 border, Jerusalem’s “holy basin” and refugees left comparatively small gaps, boiling down to a disagreement over the fate of three large settlements and the number of Palestinian refugees who would be allowed back into Israel proper.

Obama’s blueprint would declare an American position on how such gaps would be closed. He would take into account the contiguity and economic cohesion of a Palestinian state and Israeli and Palestinian security concerns, and offer guarantees and sweeteners from the international community. Without a carefully stipulated blueprint of this kind, calls for international recognition of a Palestinian state “in the 1967 border” are meaningless.

What’s holding the president back? Some are counseling that Israelis and Palestinians must “own” the deal. Netanyahu will reject any such blueprint, they say, and Israelis are generally drifting to the right. Abbas, for his part, may not now be popular enough to implement any deal — even one he is largely responsible for designing. So why should Obama present a blueprint and set himself up for diplomatic failure?

Such advice suggests a misguided foreign policy. Obama’s blueprint should not be aimed at getting the conflicting parties to “yes,” but at getting world powers to “agreed.” After presenting his plan to the Quartet, Obama should seek endorsements from one O.E.C.D. leader after another (diplomats in Jerusalem tell me the E.U. Foreign Minister Catherine Ashton is just “waiting for the word from Washington”).

An Obama blueprint should be declared in the spirit of the Arab League Initiative of 2002. It should be endorsed in advance by key U.S. Senate leaders, such as the chairman of the Foreign Relations Committee, John Kerry.

In crystallizing an international consensus regarding what peace should look like, a blueprint will create ambient pressure on the parties. It would start a new international conversation and provide a utilitarian benchmark, like the U.N. Partition resolution of 1947.

It would be a signal to Palestinian youths that an internationally backed state is, in effect, on the horizon; that in seeking unity between Fatah and Hamas, they should continue to empower the Palestine Authority to enter into international agreements and honor Abbas’s call to refrain from political violence and abhor acts of terror.

A blueprint would have enormous impact on Israeli politics, too. It would empower the moderate Israeli political parties — Kadima, Labor and the rest — to wrest back the political center from the parties of Greater Israel — Netanyahu’s Likud, Avigdor Lieberman’s nationalists and the religious.

The Israeli center — made up of Russian immigrants, non-Orthodox Mizrahi Jews, young people close to the army — is driven by fears as much as by hopes. Like “independent” voters in America, they flock to avoid what the media depict as naïve and dangerously against the current.

A blueprint, backed by everyone from German Chancellor Angela Merkel to Indian Prime Minister Manmohan Singh, would allow Israeli globalists to argue that the die is cast; that the situation in Gaza must be changed; that they alone can preserve relations with Washington and save Israel from international isolation. Obama could drive home the force of world opinion by visiting Jerusalem and Ramallah — perhaps addressing a mass rally in Tel Aviv, the heart of Israel’s globalization.

There are risks. Machiavelli wrote that great leaders must be prepared to be feared as well as loved. Obama must continue to risk making world opinion fearsome. But if he misses this opportunity, ostensibly to pursue some safer political course, moderates on both sides will lose.

The status quo means yet more settlements — and a pathetic American record of trying to halt them. Worse, it will mean Balkan-like violence enveloping the parties; every Palestinian bomb or missile, every Israeli Army assassination or errant shell, will pull more moderates to the extremes. Abbas told me he will resign if there is no tangible progress by September.

Obama will lose, too. Instead of becoming the region’s statesman, the author of a plan endorsed by global powers, Obama will run for re-election having alienated the Arab square without reassuring American circles supporting the Netanyahu government.

America, Obama concluded in his speech, must lead “support for a set of universal rights, including the freedom for people to express themselves and choose their leaders ... governments that are ultimately responsive to the aspirations of the people.” He does not have much time.