The framework agreement announced this week between Iran and the major powers isn't a formal accord on Iran's disputed nuclear program but rather a broad statement of principles that eventually could form the basis for one. Months more of hard bargaining will be needed to work out the details of how those principles translate into a final agreement acceptable to both sides. But the fact that negotiators appear to have cleared this first major hurdle is a hopeful sign that the goal of preventing Iran from developing nuclear weapons through diplomatic means is achievable.

The basic outlines of the deal call for Iran to shut down all but about 5,000 of the 19,000 centrifuges it has built to enrich uranium, and to modify its reactor at Arak to render it incapable of producing plutonium, another bomb fuel. The spent fuel from the Arak reactor would be shipped out of the country, and Iran would be prohibited from enriching uranium to more than 3.7 percent purity, far less than the 90 percent needed to build a bomb. The accord would also limit how much fissile material could remain in the country.


To make sure Iran didn't cheat, its facilities would be subjected to what would be one of the strictest international monitoring and inspection programs ever devised to detect violations. American officials say that if Iran failed to hold up its end of the bargain the world would have ample time to react — at least a year — before Iran could reconstitute its program and produce a bomb. In return, the U.S. and its negotiating partners — Britain, France, Russia, China and Germany — would gradually lift international sanctions that have crippled Iran's economy and forced it to the bargaining table.

The framework agreement had barely been announced when diverging interpretations of what it meant began emerging from the Iranian and U.S. sides. A State Department fact sheet issued to the media claimed Iran would have to dismantle or destroy thousands of centrifuges it was barred from using over the first 10 years of the deal, while Iran's foreign minister, Mohammad Javad Zarif, insisted he had agreed to nothing of the sort. Mr. Zarif, in turn, told a press conference in Switzerland that Western sanctions would be lifted immediately upon the signing of a final agreement in June, but the State Department document indicated sanctions would be lifted gradually and only after Iran proved it was abiding by the agreement.

It's not particularly surprising that the two sides are spinning the outcome of talks for the sake of their own domestic audiences. More importantly, even if the details are eventually worked out, it's not a perfect agreement from either side's point of view. The U.S., for example, initially wanted to dismantle Iran's nuclear program entirely; what it got was a continued freeze on that program for at least another 10 to 15 years. For their part, the Iranians insisted they would never surrender their right to enrich uranium; instead they will have to accept strict limits on how much they can enrich and a total ban on weapons grade material. Neither side got all it wanted, but that was to be expected as the price of any accord.

The deal outlined in the framework agreement still faces stiff opposition from critics in Tehran and Washington who believe their side's negotiators gave up too much. Mr. Zarif will have a hard time convincing hard-line members of Iran's regime that the prospect of a lifting of sanctions is worth limiting Iran's uranium enrichment activities (though ordinary Iranians, who have suffered most from the sanctions, were openly rejoicing in the streets over news of the accord). Similarly skeptical members of Congress are following the lead of Israeli Prime Minister Benjamin Netanyahu, who warns darkly that any agreement that lets Iran retain its nuclear infrastructure is a "bad deal."

Mr. Netanyahu told Congress last month that the U.S. should walk away from anything less than a total capitulation by the Iranians, saying they would come back to the table eventually because they need an agreement more than the U.S. does. But it's not likely Iran would ever agree to totally dismantle a program they've spent the last 30 years building. It's more probable it would simply move as quickly as possible to expand the program and resume its dash to develop a bomb. In that case the U.S. might find itself with no other choice than going to war with Iran.

Even if that didn't happen right away, the Sunni Muslim-led governments of Saudi Arabia, Egypt, Turkey and the Gulf Arab states would feel pressure to start their own nuclear programs, touching off a sectarian nuclear arms race with Shiite-ruled Iran in one of the most volatile regions on the planet, with potentially disastrous consequences.

What the pact, if finalized, gives the U.S. is path forward that doesn't inevitably lead to war. And make no mistake, the cost of war with Iran would be substantial, dwarfing in scale wars in Iraq and Afghanistan. A diplomatic solution is far preferable. There are still many things that remain unclear about the preliminary accord, but the U.S. must seize the opportunity it presents to reach a longer-term agreement that both sides can live with.