Tread lightly. Photographer: Behrouz Mehri/AFP/Getty Images
Tread lightly. Photographer: Behrouz Mehri/AFP/Getty Images

Iran's diplomats understand perfectly well what a Republican-controlled U.S. Congress could mean for them: more sanctions and less compromise. So the pressure is on to get an agreement in the ongoing talks over Iran's nuclear program before the Nov. 24 deadline.

When the deadline arrives, however, there will probably still be disagreements. If so, Iran and the U.S. should keep talking -- and the new U.S. Congress, which takes office in January, should be made to understand that new economic sanctions are a terrible idea. They would destroy the best, if imperfect, hope of delaying Iran's progress toward building nuclear weapons.

Iran's Nuclear Plan

President Barack Obama's carrot-and-stick strategy has already proved productive. The current negotiations are based on a year-old temporary agreement, the terms of which gave Iran limited sanctions relief but left intact trade restrictions that have halved Iran's oil exports and helped drive inflation above 30 percent. In exchange, Iran halted production and reduced stocks of 20 percent enriched uranium -- the most worrying kind -- and capped stockpiles of lower-grade fuel. It also began allowing stricter inspections, stopped work on its heavy-water reactor at Arak, and stopped installing (though not developing) new enrichment capacity.

As a result, Iran now has less fuel that it could potentially enrich to weapons grade than a year ago. Without the talks, it would have had more. Introducing new U.S. penalties now would break the terms of this arrangement and, in all probability, Iran would go back to producing fuel as fast as possible.

Source: International Atomic Energy Agency.
Source: International Atomic Energy Agency.

The unspoken truth is that no diplomatic deal can end Iran's program, or guarantee it never gets the bomb. The purpose of the talks, and of any agreement they might produce, is to delay and hinder Iranian progress. After a decade of international pressure, it is clear the Iranians will never give up all capacity to produce nuclear fuel; they still want to be able to build a bomb.

To many opponents in Congress, that's reason enough to ramp up sanctions and stop talking. A letter to Secretary of State John Kerry from 354 members of Congress, for example, demands that U.S. negotiators focus on getting Iran to live up to commitments to answer past questions about its suspected weaponization program. But forcing a confession from Iran is not the top priority. Slowing the weapons program is.

The alternatives to Obama's sanctions-plus-diplomacy approach are two: sanctions alone, or airstrikes. Neither of these would end Iran's nuclear-weapons program for good. On the contrary, they would probably accelerate Iran's bid for the bomb and undermine critical support for sanctions in Europe.

So long as Iran sticks to the restrictions on its enrichment program, and the current sanctions remain in place, there is no hurry to end this negotiating process. What matters is getting the right deal. Iran's nuclear program is largely frozen. At the same time, Iranian society is gradually becoming among the least religious and least anti-American in the Middle East. Yes, the conservative regime remains hostile and committed to creating a nuclear weapons capability. Yet it also needs a deal to keep its growing consumer society happy.

At best, a little posturing from newly empowered Republicans in the U.S. Congress may push the negotiating process along. But ultimately, everyone will be better off if hawks in Washington and Tehran alike stay out of the way.

To contact the senior editor responsible for Bloomberg View's editorials: David Shipley at davidshipley@bloomberg.net.