Do the Iran deal. Defeat the barbaric marauders of Islamic State. In the fragmenting mayhem of the Middle East, these must be the American and Western priorities.

They are objectives rooted in the strict Western interest. An Iranian nuclear accord lasting at least a decade that ring-fences a fiercely monitored and strictly limited enrichment program compatible only with civilian use is not an ideal outcome, but it is the best conceivable outcome of protracted talks that have already reversed the nuclear momentum in Iran and established a bridgehead between Washington and Tehran.

Any such agreement . and the deadline is imminent . must leave Iran a minimum of a year from any ‘‘break-out’’ to a bomb. The alternatives are far worse. Centrifuges and enrichment levels would resume their upward curve. War drums would beat again despite the fact that calls to attack Iran are an irresponsible invitation to disaster.

American or Israeli bombs on Persia (or both) would have all sorts of ghastly consequences, but the fundamental argument against such folly is that they would cause no more than a hiccup in Iran’s nuclear program before spurring it to renewed and unmonitored intensity. This would be war without purpose, or war on false pretenses. We’ve seen enough of that.

Iran is a hopeful and youthful society. Nurture the hope. Don’t imprison it. A deal lasting 10 years would condemn Iran and America to a working relationship over that period. I use the word ‘‘condemn’’ advisedly. It would not be pretty. In fact it would be ugly. There would be plenty of disagreements.

But jaw-jaw is better than war-war. Much can be achieved with nations that have fundamental ideological differences with the United States; look at the history of Chinese-American relations since they resumed in the 1970’s. During the next decade the Islamic Republic is likely to go through a leadership change. Its society is aspirational and Westward-looking. ‘‘Death to America’’ has become a tired refrain. What these elements will produce in terms of change is unpredictable, but the chance of positive developments is enhanced by contact and diminished by punitive estrangement of Tehran.

Would it be preferable that Iran not have the nuclear capacity it has acquired? Sure. Can there be absolute guarantees a deal would be honored? No. But diplomacy deals with the real world. The toughest, most important diplomacy is conducted with enemies. Opponents of an accord have offered no serious alternatives.

Only elementary knowledge of Iran is needed to know that sanctions will never bring this proud nation to its knees. It would rather starve than cave. What better assures Israel’s security, a decade of strict limitation and inspection of Iran’s nuclear program that prevents it making a bomb, or a war that delays the program a couple of years, locks in the most radical factions in Tehran, and intensifies Middle Eastern violence? It’s a no-brainer.

I like the current inconsistencies in President Obama’s Middle East policy. Some ask how it can make sense to pursue an Iran deal while backing Arab states, principally Sunni Saudi Arabia, in a campaign against Iranian-backed Houthi forces in Yemen. To which the answer is first that interests drive foreign policy, not the pursuit of consistency (Stalin was once the most effective of American allies); and second that America is making it clear to Iran, even before any possible deal, that it will not abandon its allies, including Egypt and the Saudis, just because a nuclear agreement has been reached. This is an important message. The United States will oppose Iran where its interests and those of its allies demand that, deal or no deal.

One area where American and Iranian interests broadly coincide is in defeating Islamic State, the latest expression of the metastasizing Salafi Islamist ideology of murderous hatred toward Western civilization that produced 9/11 and recent murderous rampages in Europe. Islamic State is also a Sunni revanchist movement in Iraq and Syria, directly opposed to Shia Iran. There is nothing uplifting about the overlap in American and Iranian interests, but that does not make it any the less important. Rolling back Islamic State requires at least tacit Iranian cooperation.

America cannot stop the Sunni-Shia schism in the Middle East that its invasion of Iraq exacerbated. It cannot rebuild the Sykes-Picot order, or the borders that went with it. It cannot reverse its failure to prevent the worst in Syria (which will forever blot Obama’s record), nor its failure, outside Tunisia, and particularly in Egypt, to nurture the hope of the Arab spring for more representative societies freed from the paralyzing (and mutually reinforcing) confrontation of dictatorship and Islamism. It cannot prevent the violence inherent in all these developments. Nor should it hide its eyes from the fact that this violence will last a generation at least.

This is not cause for despair but reason to concentrate, fiercely, on the two attainable objectives that matter most now.