This threat is aimed at Europe more so than at the U.S., although their problem will become our problem if they can’t reach some economic accommodation with Iran quickly. If not, what does Trump propose to do? Both he and Khamenei have ruled out talks, and I suspect Khamenei’s less willing to budge on that than Trump is. (Even John Bolton is willing to entertain diplomacy with Iran now, for cripes sake.) Meanwhile, Trump has reportedly all but ruled out war, recognizing that it would betray his pledge in 2016 to put America first by reducing foreign entanglements.

So if Iran starts to increase enrichment again, what’s the plan to make them stop? More sanctions? Hand the baton to the IAF and wish them luck? Look the other way and hope that a diplomatic breakthrough will arrive before Iran has a stash of weapons-grade uranium?

Remember, although Trump has withdrawn the U.S. from Obama’s nuclear deal and ramped up sanctions, the deal remains in effect momentarily between Iran and the European signatories. America’s sanctions were aimed at bringing “maximum pressure” on Iran, and they’re succeeding; the economic pain has driven Iran to demand that Europe provide some relief ASAP or else it’ll quit the deal too. That helps explain the spate of mysterious tanker attacks in the Gulf of Oman lately, as well as the news last week that Iran has increased production of low-enriched uranium. They’re saber-rattling, warning the Europeans that they might go rogue — including on nuclear development — if the money doesn’t start flowing soon. Today’s news is the latest rattle:

Iran is ramping up enrichment of low-grade uranium and will pass the limit it is allowed to stockpile under the nuclear deal in 10 days, a spokesman for the Iranian atomic agency announced Monday…

After exceeding the limit, Iran will accelerate uranium enrichment to 3.7%, Kamalvandi said — above the 3.67% mandated by the nuclear deal. Enrichment at this percentage is enough to continue powering parts of the country’s energy needs, but not enough to ever build a nuclear bomb…

Israeli Prime Minister Benjamin Netanyahu, who is perhaps the most outspoken critic of the nuclear deal, called on the international community to immediately impose sanctions on Iran if it violates the 2015 agreement.

Netanyahu wants “snapback sanctions” applied under the terms of the deal if Iran violates it, but of course Iran will claim that America violated the deal first by withdrawing, before Iran began to increase enrichment. Europe will be sympathetic to that argument since it fears Iran going rogue and wants to keep the deal intact to discourage that. In fact, the European signatories have already created a financial mechanism called Instex that aims to enable trade with Iran while evading U.S. sanctions — although, per the Atlantic, the U.S. has threatened to sanction Instex too. (Iran’s counterpart to Instex is also under threat of sanction, of course.) That’s a threshold gut-check question for Trump and Congress: Are they inclined to look the other way at Instex if it begins trading with Iran? If they’re serious about “maximum pressure,” they should sanction it and try to choke Iran off completely from trade with the west — although in that case, a desperate Iran might seek a nuclear “breakout,” enriching uranium to high levels and maybe trying to build a bomb.

If instead the U.S. allows Instex to trade with Iran without sanction, then the “maximum pressure” campaign has a giant loophole. Iran’s economy will be bolstered, not crushed. But that’ll also likely convince Tehran to dial back enrichment and maybe calm down in the Gulf, averting a giant foreign-policy headache before the election. Which way does Trump want to go on this?

Note that Iran’s not just threatening to produce more low-enriched uranium beyond the 300 kg they’re allowed under the terms of the nuclear deal. They’re threatening to refine the uranium they’ve already stockpiled to higher levels, a prerequisite to building a bomb:

He also raised the specter of increasing its enrichment levels, saying Iran needs 5% enriched uranium for its nuclear power plant in southern Iranian port of Bushehr and 20% enriched fuel for its Tehran research reactor…

The danger, nuclear nonproliferation experts warn, is that at 20% enrichment, only a fraction of atoms need to be removed to enrich up to weapons-grade levels of 90%.

Assume Instex is sanctioned, Europe decides that it would rather trade with the U.S. than Iran, and Iran ends up without an economic lifeline. In Bolton’s dream scenario, the Iranian people revolt over their sudden economic hardship, the mullahs are deposed, the new liberal interim Iranian government agrees to give up nukes forever, and Trump hosts the interim president for a grip-and-grin and KFC at the White House. In the nightmare scenario, the economic hardship begins to tilt more Iranians towards the hardliners within the regime, the hardliners insist on more provocations in the Gulf and higher levels of enrichment, and Iran sets out to amass enough weapons-grade uranium for a bomb. The good news is that, even in the nightmare scenario, this can’t happen overnight: Last year the Times spoke to experts and estimated that it would take Iran at least a year, perhaps considerably longer, to first stockpile enough low-enriched uranium and then to refine it to bomb-grade levels. The bad news is that U.S. intelligence about Middle Eastern countries’ nuclear capabilities has traditionally been, well, problematic.

But maybe that’s the plan. Isolate Iran economically, let ’em attempt a nuclear breakout, and trust that the economic pain will lead them to beg for mercy and negotiations before they have the HEU they need in hand. (Or before Israel acts.) How lucky do you feel?