U.S. officials have very good reason to be wary of Iran’s bona fides. In 2009, they reached a deal with Iranian negotiators to send the stockpile of highly enriched uranium out of the country — only to see the ayatollah repudiate it. As Ray Takeyh, an Iran expert with the Council on Foreign Relations puts it, “Khamenei has created a politics where it’s hard for him to compromise.” But so has the United States. Anyone who watched Chuck Hagel’s confirmation hearing knows that it is an article of faith in Congress — and pretty much a bipartisan one — that Iran is a faithless, illegitimate terrorist state that will be deterred from building a bomb only by the threat of massive attack. Had Hagel been foolish enough to suggest that the United States offer to reduce sanctions in exchange for Iranian concessions, the White House would have had to find a new candidate for defense secretary.

It’s the U.S. Congress that arguably holds the high cards, though the White House put them in its hands. The most potent sanctions are legislated, and have been written in such a way that they will be very hard to unwind. Obama can waive them for up to six months. But the ayatollah is not about to make irreversible decisions in exchange for six months of relief.

The White House is thus stuck between Tehran and Capitol Hill. And it can’t live long with the current stalemate. After all, Obama has said that “containment” is not an option. He is hoping that the combination of economic pain and fear of military action will bring Tehran to its senses. If it doesn’t, the president has said that he is prepared to use force. Perhaps he feels that just as spurned engagement served as the predicate for tough sanctions, so would failed negotiations lay the predicate for a broadly supported strike against Iran’s nuclear facilities. Iran left us no choice, he might say, as the bombers fly.