It was a shame but not all that surprising today when the awaited encounter between U.S. President Barack Obama and his Iranian counterpart Hassan Rohani didn’t happen at the United Nations. It seems Obama offered to shake Rohani’s hand, but the invitation was declined. The last time leaders of the two countries met was 36 years ago -- during the reign of Shah Mohammed Reza Pahlavi. He’d been installed in a U.S.-backed coup against a democratically elected leader, only to be overthrown in 1979 by Islamic revolutionaries who held 52 Americans hostage for 444 days.

In other words, there’s a lot of history here -- the kind that makes opening a new chapter of less hostile relations difficult. Over the years, what each country wants from the other hasn’t much changed. The Iranians want to be treated with respect, and the Americans want Iran to behave respectably, especially when it comes to Iran’s nuclear program.

The Iranians say this program exists only to produce electricity and pursue medical research. They say they’ve no intention of building nuclear weapons and have a right to nuclear technology, including uranium enrichment. As a relatively prosperous and scientifically advanced country, they say, Iran shouldn’t be forced to rely on others for part of the nuclear fuel cycle: It’s a matter of national pride.

Fine, so long as Iran meets its obligations under the Nuclear Non-Proliferation Treaty and submits its nuclear installations to inspection by the International Atomic Energy Agency. As we’ve argued before, the U.S. should relieve Iranian anxieties by stating that it can live with a limited Iranian enrichment capacity. That would go a step beyond Obama’s statement to the UN today that Iran has the right to civilian nuclear power.

At the same time, if the Iranians want to be believed when they say their program is innocuous, they would do well to stop insisting, as Rohani has in recent days including in his own speech to the UN, that Iran has never sought nuclear weapons. The U.S. and its allies collected strong intelligence showing Iran had such a program until it halted the work in 2003. Iran needs to acknowledge the past program and allow the IAEA to investigate sites suspected of housing it. When South Africa renounced its nuclear-weapons program, it initially tried to hide the full story, which bred mistrust. Only when it declared in 1993 that it had developed nuclear bombs and invited the IAEA to verify its statements did its government gain credibility.

The Iranians may think they can’t afford to be that open -- perhaps fearing that if they acknowledge having ever tried to develop the bomb, the U.S. will seize on the admission as an excuse for pursuing regime change. That’s understandable. On top of the U.S. history of meddling, there’s the fact that undermining the Iranian government has become an explicit goal of some members of Congress: They support increasingly severe sanctions regardless.

Obama told the UN that the U.S. doesn’t seek regime change, but it will take more than that to convince the Iranians. Congress will have to stop tightening the squeeze on Iran and allow the diplomats to test whether the punishments already in place have created an opening for meaningful talks. A settlement could offer the lifting of sanctions in stages as Iran meets its IAEA obligations. That would be a good result -- but to get there, each side must first convince the other that it’s serious.

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