The preliminary agreement over Iran’s nuclear program — a deal reached after years of patient work building sanctions and pushing negotiation — is a critically important first step toward a peaceful resolution of a very tough problem. It ought to be applauded and supported, not sabotaged.

Because basically, you’ve got two possible approaches. This, or war.

Critics of the Obama administration may like to pretend otherwise, but listen closely to their arguments. They have none. Sure, Israeli Prime Minister Benjamin Netanyahu and others would prefer that as part of this six-month temporary deal, Iran had agreed to surrender unconditionally on every point. However, they offer no rationale for thinking that goal would be achievable. No Iranian government at all reliant on the popular support of its people would ever be able to agree to that, and as politicians with their own constituencies, Netanyahu and others know that.

The truth is, the world leaders got a great deal. The United States, Russia, China, France, Great Britain and Germany have agreed to free less than $7 billion in Iranian foreign reserves trapped in the international banking system. And that’s about it. The arms embargo remains in full effect. The ban on Iranian participation in international banking remains. The very tight lid on Iranian oil sales also remains in effect. None of that changes.

In return, Iran agrees to dilute or destroy its stocks of highly enriched uranium. Its stockpile of uranium enriched to 20 percent would fall from more than 400 pounds to zero. In addition, it will not expand any of its production capability. And it will allow U.N. inspectors total, daily, unannounced access to all of its nuclear facilities, from the mines where raw uranium is dug to its highly sophisticated enrichment facilities.

Cynics question whether Iran will live up to that agreement. Well, we’ll see. That’s what these next six months are all about. If the cynics prove correct and the deal is breached, talks cease and even tougher sanctions become likely.

However, most people — including me — were dubious when Syria announced that it would open its chemical-weapons program to the outside world, yet it has done so, and its stockpiles and production facilities are being destroyed with surprising speed. More than a decade ago, a lot of people were skeptical that Saddam Hussein would give free rein to inspectors, but he finally did so, allowing them complete and unfettered access.

In that case, of course, war in Iraq still came anyway, because war, not disarmament, had been the real goal from the beginning. I would hope that we have learned something from that experience.

Any war short of the invasion and occupation of Iran would not produce the verified destruction of its stock of nuclear material already purified to the 20 percent level, as this deal does. War would also all but guarantee that in the long run, Iran gets the bomb. It would gut its moderates and confirm the argument of its radicals that only with a nuclear weapon would Iran be protected from outside intervention.

Finally, it’s important to note that a temporary deal is no guarantee of a permanent resolution. Hardliners in both countries are going to try to squelch it, and we do not know yet whether Iran is truly willing to surrender its nuclear ambitions in return for an end to sanctions. But it would be foolish not to try to find out.