Three decades of hostility between the US and Iran have tangled politics and deep mistrust with technical issues about Iran's rights and obligations as a signatory of the Nuclear Non-Proliferation Treaty (NPT). A US-European package of incentives requires total suspension of enrichment as a pre-condition to even begin negotiation – a stance many argue is untenable.
"Right now, Iran is holding the cards," says Mr. Levi, author of the recently published On Nuclear Terrorism. "The odds of us getting zero enrichment without a military strike are low…. If we can't muster much additional pressure, I don't see any solution that does not involve limited enrichment. And if we are going to accept [that], we want to put as many constraints on it as we can."
Experts say that to be effective, any joint program would depend on – among other restrictions – Iran accepting the additional protocol of the NPT, which enables intrusive, short-notice inspections.
Iran was praised in the February report by the UN's nuclear watchdog agency for taking such open steps to resolve several outstanding issues, but says it will not accept the protocol wholesale until its case is removed from the Security Council agenda.
"Now Iran knows the technique and technologies. Iran has the base, and when a country has a base you can't change everything – you must deal with it," says Sadegh Kharazi, Iran's former ambassador to Paris.
"Now the leadership of Iran is ready to make a decision – a comprehensive decision," he says, adding that Iran demonstrated seriousness by resolving six longstanding issues identified with the International Atomic Energy Agency (IAEA) last year. Another window may have opened since the recent US National Intelligence Estimate found that Iran had halted a nuclear weapons program in 2003.