Remember that splashy report last week about the U.S. maybe possibly conceivably allowing Iran to retain 6,500 centrifuges for enrichment, a number far greater than Iran hawks in Congress would be comfortable with? That leak allegedly came from Netanyahu’s office, designed to squeeze Obama as he gets closer to a final deal with Tehran. U.S. negotiators criticized the leak — for being incomplete on the details, not for being wrong.

Now we know why.

The United States and Iran are working on a two-phase deal that clamps down on Tehran’s nuclear program for at least a decade before providing it leeway over the remainder of the agreement to slowly ramp up activities that could be used to make weapons…

One variation being discussed would place at least 10-year regime of strict controls on Iran’s uranium enrichment program. If Iran complies, the restrictions would be gradually lifted over the last five years of such an agreement.

Iran could be allowed to operate significantly more centrifuges than the U.S. administration first demanded, though at lower capacity than they currently run. Several officials spoke of 6,500 centrifuges as a potential point of compromise, with the U.S. trying to restrict them to Iran’s mainstay IR-1 model instead of more advanced machines.

It would also be forced to ship out most of the enriched uranium it produces or change it to a form that is difficult to reconvert for weapons use. It takes about 1 ton of low-enriched uranium to process into a nuclear weapon, and officials said that Tehran could be restricted to an enriched stockpile of no more than 300 kilograms (about 700 pounds).

So they are talking about 6,500 centrifuges! More specifically, 6,500 IR-1 centrifuges, a 1970s-era technology based on a design by Pakistan’s Abdul Qadeer Khan. Like a 70s-era car, the IR-1 will get you where you want to go if kept in good working order but it’s far less efficient than more modern models like the IR-2, which can enrich uranium at five or six times the speed of the IR-1. If Iran agrees to use first-generation centrifuges going forward, they’d necessarily be agreeing to extend the time it would take them to produce weapons-grade uranium once they decide to go full-throttle towards building a bomb. And remember, that’s the White House’s goal here — buying time. Obama long ago abandoned the idea of getting Iran to give up its nuclear program. The mullahs can’t do that without it being seen at home as a capitulation to the west; since day one they’ve insisted on their right to enrich uranium for, ahem, peaceful energy purposes. Obama’s compromise is to let them do that provided that they slow down and let UN nuclear inspectors watch the process closely, to ensure that Iran’s not secretly enriching uranium at bomb-grade levels at hidden sites across the country. If he can get them to agree to use older, slower centrifuges, it’ll extend the “breakout” period, i.e. the time it takes to enrich a supply of uranium from the low purity needed to fuel reactors to the very high purity needed to make nuclear bombs. The longer the breakout period is, the more time the U.S. and Israel would have to intervene with an air attack before Iran’s bomb is ready. Netanyahu thinks this is a sucker’s game since it’s difficult for even the best foreign spy agencies to know just how much uranium Iran has and how many secret enrichment sites they might operate. But Obama, go figure, thinks it’s acceptable.

So we’re playing for time on the breakout period. We’re also playing for time geopolitically, partly so that Obama can claim some sort of victory for legacy purposes — Iran won’t have built any bombs (so far as we know) by the time he left office, will it? — and partly because 10 years is a long stretch in Middle East, especially at this particular historical moment. Ten years ago, the big question about Syria was whether it would continue to occupy Lebanon; ten years later, the question is whether Syria will continue to exist in any meaningful way. Maybe Iranians will overthrow the mullahs by 2025. Or maybe the halting American-Iranian detente we’re engaged in right now will blossom into full diplomatic relations, with Tehran agreeing as a gesture of goodwill to engage only in non-nuclear terrorism against the west. (Peace in our time!) Or maybe Iran will finish the job against the Sunnis in Iraq and Syria and effectively take those countries over, portending lord knows what for its nuclear ambitions. Job one here for Team Hopenchange is kicking the can and a 10-year deal does that. The truly important part of the agreement, in my ignorant understanding, is how much access western nuclear inspectors get to suspect sites within Iran. The more reluctant Iran is on that point, the surer the indication that they’re planning to cheat and go for a bomb sooner rather than later.

Now, good luck finding at least 21 Republican votes in the Senate to get the 67 needed to ratify this deal. Or is our leader preparing to executive-action his way out of that constitutional requirement too?