And at the top of the system is Iran’s supreme leader, Ayatollah Ali Khamenei, a still-young 73, bitterly anti-American, devoted to the Islamic Revolution and, as a clerical politician, famous for being indecisive.

Not the ingredients you’d choose for a complicated set of negotiations.

Is there a way forward?

“It’s important to start small, and use small steps to build trust,” said Thomas Pickering, a former top State Department official who has engaged in unofficial talks with Iran (and who recently appeared together with Khazaee at New York’s Asia Society).

Don’t shoot for big, splashy agreements with Tehran — that just gives opponents on both sides something to shoot at. Besides, the idea of a grand bargain with the United States appears to make Khamenei nervous.

The pattern of the last few months, in which Iran has made encouraging moves outside formal negotiations, may offer a lesson. “Don’t ever insist that they make concessions publicly,” said Limbert. “They may take steps that we like, but they’re never going to admit that they did it under pressure.”

Above all, said Limbert, “don’t give up. It’s not going to work the first time.”

The second half of 2013 may turn out to be a promising window for diplomacy with Iran. The Iranian presidential election will be over. The U.S. presidential election is already over. Iran’s action in converting enriched uranium to nonmilitary reactor fuel has reduced pressure from Israel for immediate action.

At that point, the biggest danger may be political gridlock in Tehran, abetted by indecisive leaders who hesitate to embrace a grand bargain in the face of pressure from their zealous followers. Sound familiar?