A Reuters dispatch says that Israel’s most widely read newspaper, Yedioth Ahronoth, reported on Monday that the Obama administration had approached Iran through two European intermediary countries with a remarkable proposal. The Israeli newspaper said the United States promised to refrain from any involvement in an Israel-Iran war triggered by an Israeli attack on Iran. In exchange, said the report, the United States wanted assurances that Iran would not go after U.S. military positions in the region following an Israeli attack.

It’s difficult to fathom what to make of such a report, and there are ample reasons to question the veracity of an item suggesting the United States is prepared to embrace a diplomacy that separates itself so starkly from Israel. But, whatever its veracity, the report suggests a new reality has emerged in U.S.-Israel relations. The interests of the two countries have diverged on the question of war with Iran. This new reality is reflected also in a Time report over the weekend that the United States in February postponed a massive joint U.S.-Israel military exercise that had been scheduled for a time when U.S. concerns were growing over a unilateral Israeli military strike against Iran. The exercise, according to the report, was rescheduled for October, but Washington has severely reduced its participation, with perhaps 1,500 or even just 1,200 U.S. military personnel now scheduled to take part instead of the originally planned 5,000.

Time quotes one senior Israeli military official as suggesting the United States downsized its role to distance itself from Israel’s constant drumbeat for war with Iran. “Basically,” the official told the magazine, “what the Americans are saying is, ‘We don’t trust you.’” This raises a question: If President Obama truly believes the two countries’ interests have in fact diverged in serious ways, what can he do about it? What should he do about it?

Consider first the likely consequences of a unilateral Israeli attack on Iran—the Syrian civil war exploding into a region-wide sectarian conflict; destabilization of such nations as Bahrain, Jordan and Lebanon; obliteration of the Egyptian-Israeli peace agreement; a new Intifada in the occupied Palestinian lands; expanded terrorist activity against the West; a doubling or tripling of oil prices; a likely economic meltdown in Europe and China, with huge subsidiary damage to the U.S. economy. All of these things easily could be triggered simply by an Israeli attack on Iran; all of them likely would be worse if America got dragged into the resulting Israeli-Iranian conflict.

Second, what kind of country would America be if it ceded its sovereignty in matters of war and peace to a tiny ally that seems bent on manipulating American decision making by manipulating American domestic politics? It’s one thing to have Israel thwart America’s efforts to foster a peaceful settlement to the Israeli-Palestinian conflict, based on Israel’s perception of its own interests; it’s quite another to allow Israel to pull the United States into a war that the American people are not prepared for and that likely would severely harm America’s economic and geopolitical interests.

In political terms, the geopolitical and economic chaos that would be unleashed by such a war probably would upend any president who lacked the fortitude to prevent it. If a global recession and all of its resulting anguish could be attributed, in retrospect, to the president's pusillanimous inability to stand up to an errant ally, new opposition forces would emerge to deal a blow to the incumbent party that could last a decade or more. A good object lesson would be Woodrow Wilson, whose war decisions unleashed such devastation upon the American polity that voters in 1920 repudiated the incumbent party with a magnitude seldom seen in American history.

All of this argues for the American president—either Obama or his successor—to separate his government starkly from the Israeli government on the matter of an attack on Iran. But what about the political backlash? It would be fierce, as anti-Iran hawks and friends of Israel throughout America go on the attack. The pro-Israel lobby would mobilize, and evangelical Christians would swarm into political action like angry hornets. Journalists would speculate widely that the president had destroyed his political standing with Jewish voters. But all this would miss the big picture. On fundamental issues, the politics of national interest often trump the politics of parochial interest. The president would have to explain his action to the American people, but he would move the polls dramatically if he could explain effectively the national stakes involved—a merely restive Middle East vs. absolute chaos; at least a chance for an ongoing, if slow, economic recovery vs. the certainty of a global recession; a proud America protecting its sovereign command over decisions of war and peace vs. a country that cedes those decisions to others; presidential leadership that protects the interests of the American people vs. leadership that loses sight of such things.

The essence of the argument would have to be that it isn’t in America’s interest to go to war with Iran while the president is pursuing his regimen of economic sanctions and seeking a negotiated solution through the ongoing talks involving Iran and the so-called P5+1 (the United States, Britain, France, China, Russia and Germany). And he isn’t willing to cede to other nations U.S. decisions that could result in perhaps thousands of combat deaths for young Americans in an already stretched U.S. military.

The president would win that argument, but first he would have to demonstrate the fortitude to take it forcefully and deftly to the American people.

Such a political victory in turn would transform U.S. relations with Israel. The conventional wisdom in Washington is that interest-group politics, and particularly ethnic-group politics, drive events. That’s often true, but not when a national consensus emerges that runs counter to the parochial interests of particular groups. As Woodrow Wilson once wrote, “If [the president] rightly interpret the national thought and boldly insist upon it, he is irresistible.”

We have seen in recent years an Israeli prime minister, Benjamin Netanyahu, who sought to outmaneuver the U.S. president by mustering political sentiment against him through speeches to the U.S. Congress and to the AIPAC lobbying group. But that’s possible only if pro-Israel Americans can make the case that America’s interests and Israel’s are always identical, and thus any president who isn’t in sync with Israel’s national leadership is perforce on the wrong side of domestic politics. Of course the interests of any two nations are never always identical. And if the president successfully can convince the American people that the two nations’ interests not only can diverge but have, then the balance of influence in the relationship will change in America’s favor. And Netanyahu would have to ponder carefully whether he wants another shot at taking on the U.S. president on his own turf. That’s assuming that the diplomatic chastisement represented by the new U.S. diplomacy hasn’t led to the collapse of his government in the meantime.

So let’s assume Obama believes U.S. and Israeli interests have diverged over Iran and strongly believes his job requires him to protect his country from the consequences of an Israeli strike. What can he do about it? One possibility would be actions akin to what was reported by Yedioth Ahronoth—an understanding with Iran that America would not involve itself in any Israeli attack and would remain neutral in any subsequent Israel-Iran war. This would have the virtue of protecting American interests without impinging upon Israel’s own range of options in protecting itself from perceived threats. But it seems unrealistic to think the Iranians would believe America would in fact remain aloof from Israel in such circumstances or that it could not bring to bear sufficient pressure to forestall such an Israeli attack. This seems like a nonstarter.

That leaves what might be called the Brzezinski option, named after former White House national-security adviser Zbigniew Brzezinski, who has argued for a U.S. stance that declares firmly and clearly that America will not accept an Israeli attack on Iran because the consequences would be “disastrous” for America and the world—and for Israel too. As Brzezinski points out, polls in Israel show a large majority there opposes a unilateral Israeli strike, particularly if it would harm Israel’s relations with America, and hence a firm American stance would generate serious political pressures on Netanyahu within his own country.

Of course, it isn’t clear that Obama or any future president actually will see events with sufficient clarity to conclude that the United States and Israel are on divergent paths on the matter of Iran. But they are. And, when it comes to America’s vital national interests—particularly when the expenditure of American blood is on the line—the president’s job is to see events with crystal clarity.

Robert W. Merry is editor of The National Interest and the author of books on American history and foreign policy. His most recent book is Where They Stand: The American Presidents in the Eyes of Voters and Historians (Simon & Schuster, 2012).