The biggest set of obstacles to achieving an agreement to limit Iran's nuclear program involves each side's inclination to believe the worst regarding the other side's intentions. A major body of opinion in the United States holds that Tehran is hell-bent on acquiring nuclear weapons and that any indications to the contrary—including the Iranian denials of an intention to build a nuclear weapons, the fatwas by the supreme leader saying that such weapons are un-Islamic, the continued adherence to the nonproliferation treaty, the acceptance of international inspectors, and the Iranians' restraint in accumulating any stockpile of medium enriched uranium—constitute posturing, lying or stalling. A corresponding body of opinion in Iran, which may include the supreme leader, believes that the United States is determined to achieve regime change and intends to squeeze and punish Iran until such change is indeed achieved. The Iranians have been given plenty of reason to believe that, and so when they see or hear something about the United States instead wanting to reach agreements with the Islamic Republic, the Iranians suspect that this is just posturing, lying or stalling.

With such a deep hole of distrust out of which to dig, the results of the negotiations in Kazakhstan this week between Iran and the P5+1 were encouraging. The P5+1 had the good sense to make at least modest changes in its previous negotiating position, by putting a bit more sanctions relief on the table and reframing a key demand regarding one of the critical Iranian nuclear facilities. The parties still have a long way to go, especially regarding the sanctions side of things. But the Iranians strove to put a positive spin on the results. The movement in the P5+1 position may have been small, but it caught their attention. When the chief Iranian negotiator, Saeed Jalili, made his customary post-round appearance before the press, this was the first time he did so without displaying photographs of any of the assassinated Iranian nuclear scientists.

With this situation of discernible but reversible progress at the negotiating table, the worst thing that anyone—especially anyone who supposedly favors restricting Iran's nuclear program to preclude an Iranian nuclear weapon—could do at this moment would be anything that stokes the Iranian suspicions about true U.S. intentions. But that is what is being done right now in Congress, with two draft measures in particular. One is a bill—a kind that members by now could write in their sleep—to pile still more sanctions on Iran. Probably even worse is a Senate resolution introduced by Lindsey Graham and Robert Menendez that for most part is just another expression of Congressional love for Israel but that ends with a clause that gives a green light for Israel to launch a war against Iran.

That latter resolution would be extraordinarily inappropriate even if it came at a less promising and critical time—a “turning point,” according to Jalili—than now. The resolution condones what would be an act of aggression that, despite supposedly being taken in the name of nuclear nonproliferation, would be committed by a state that has long had an arsenal of nuclear weapons that is totally outside any international control regime, against a state that has no such weapons and hasn't even decided it wants to build any. The resolution also means happily surrendering to a foreign state the decision to start a war that would have serious repercussions for the United States.

If Iran took comparably provocative steps in the wake of a negotiating round, many voices in the United States would be yelling about how this shows how hostile are Iranian intentions, how Iranians are not serious about negotiating an agreement, and how the United States must respond by making its own posture even more hard line and inflexible. We should not be surprised if when the provocation is in the other direction, Iranians might react similarly.

Bashing of Iran and coddling of aggressive Israeli action is now second nature to many members of Congress, who need no additional stimulus for that sort of thing any more. But AIPAC is giving them such a stimulus anyway. What better time than now, with AIPAC's annual policy conference coming up next week, for the organization to try to demonstrate anew that it hasn't been cowed by the Hagel nomination contest, in which it decided early to fold what it correctly determined was a losing hand.

Abba Eban famously observed that the Palestinians never miss an opportunity to miss an opportunity. Unfortunately we are getting to where we might be able to say the same thing about the United States with regard to Iran. The biggest past instance of missing an opportunity came in 2002, when a brief period of fruitful U.S.-Iranian cooperation was ended by George W. Bush's declaration of the axis of evil. With initiatives such as we are seeing today on Capitol Hill, there might be another big missed opportunity in the making.