In diplomacy, always leave your adversary an honorable avenue of retreat.

Fifty years ago this October, to resolve a Cuban missile crisis that had brought us to the brink of nuclear war, JFK did that.

He conveyed to Nikita Khrushchev, secretly, that if the Soviet Union pulled its nuclear missiles out of Cuba, the United States would soon after pull its Jupiter missiles out of Italy and Turkey.

Is the United States willing to allow Iran an honorable avenue of retreat, if it halts enrichment of uranium to 20 percent and permits intrusive inspections of all its nuclear facilities? Or are U.S. sanctions designed to bring about not a negotiated settlement of the nuclear issue, but regime change, the fall of the Islamic Republic and its replacement by a more pliable regime?

If the latter is the case, we are likely headed for war with Iran, even as our refusal to negotiate with Tokyo, whose oil we cut off in the summer of 1941, led to Pearl Harbor.

What would cause anyone to believe Iran is willing to negotiate?

There are the fatwas by the ayatollahs against nuclear weapons and the consensus by 16 U.S. intelligence agencies in 2007, reaffirmed in 2011, that Iran has no nuclear weapons program.

Even the Israelis have lately concluded that the Americans are right.

Nor has the United States or Israel discovered any site devoted to the building of nuclear weapons. The deep-underground facility at Fordow is enriching uranium to 20 percent. There are no reports of any enrichment to 90 percent, which is weapons grade.

Iranian President Mahmoud Ahmadinejad has lately mocked the idea of Iran building a bomb in the face of a U.S. commitment to go to war to prevent it:

"Let's even imagine that we have an atomic weapon, a nuclear weapon. What would we do with it? What intelligent person would fight 5,000 American bombs with one bomb?"

Ahmadinejad did not mention that Israel has 200 to 300 nuclear weapons. He did not need to. The same logic applies.

And Tehran seems to be signaling it is ready for a deal.

According to the United Nations' watchdog agency, Iran recently converted more than one-third of its 20 percent enriched uranium into U308, or uranium oxide, a powder for its medical research reactor.

The New York Times also reported Thursday that Iran had proposed to European officials a plan to suspend the enrichment of uranium in return for the lifting of sanctions. By week's end, Iran was denying it.

Yet common sense suggests that if Iran is not determined to build a nuclear weapon, it will eventually come to the table.

Why? Because, if Iran is not seeking a weapon, no purpose is served by continuing to enrich.

Iran already has enough 20 percent enriched uranium for medical isotopes and more than enough 5 percent enriched uranium for its power plant. Further enrichment gives Iran nothing in the way of added security, but it does ensure that the severe sanctions will be sustained and perhaps tightened. And those sanctions are creating tremendous hardships on the Iranian people.

In two weeks, Iran's currency, the rial, has lost a third of its value. It is at an all-time low against the dollar. Iran's oil exports are down to 800,000 barrels a day, a third of what they were a year ago. The cost of food and medicine is soaring. Inflation is running officially at 25 percent. Foreign travel is drying up. Workers are going unpaid.

"We're close to seeing mass unemployment in cities and queues for social handouts," an Iranian-born economic adviser to the European Union told Reuters. "There are few alternatives for those people, and many will end up on the bread line." Last week, merchants marched on parliament and had to be driven back by police using tear gas.

An Iranian businessman in Dubai told Reuters: "Business is drying up. Industry is collapsing. There's zero investment. ... I see it with my own eyes."

In short, the oil embargo and economic sanctions, what Woodrow Wilson called the "peaceful, silent, deadly remedy," are working, and Ahmadinejad — who leaves office next year — is rapidly losing support.

So a new question is now on the table. If Iran advances ideas to demonstrate convincingly that it has no weapons program, but insists on what President Obama said he supports — Iran having a peaceful nuclear program under U.N. inspection — will America accept that?

Or will we, seeing the economic crisis deepening, make demands so humiliating no Iranian government can accept them, because our true goal is and has always been regime change?

No one would weep if the Islamic Republic fell. But this is a tough crowd that will not go quietly. If we give them no way out, only a choice between national humiliation or escalation, the hard-liners in the regime and Republican Guard will likely take the death-before-dishonor course.