It was telling that chief US negotiator, Wendy Sherman, headed straight for Israel after last week's Baghdad nuclear talks with Iran. "We updated the Israelis in detail before we updated our own government," an unnamed senior US official told the Israeli daily Haaretz.
Israel is not part of the diplomatic process of which it takes a cynical view, and insists that Iranian surrender on the issue of uranium enrichment is the only acceptable outcome. And by brandishing the threat of unilateral military action and leveraging its considerable support in Washington, Israel may have bought itself a de facto veto over what transpires in talks between the western powers and Iran.
But it's not only Israeli pressure that's driving the US position; the Obama administration itself appears to have embraced the view that the sanctions currently being implemented against Iran will be so painful that they'll bring Tehran to heel. Such leverage is not going to be squandered on confidence-building steps when they could hold out for the long-standing prize of Iranian capitulation on all uranium enrichment.
Unfortunately, many on the Iranian side believe that US President Barack Obama needs a deal more than Ayatollah Ali Khamenei does; that the US-Israeli hard line will split the P5+1 (the US, Britain, France, Russia, China and Germany); and that Washington and its European allies can ill afford a military confrontation with potentially catastrophic effects on their wheezy economies. That's why the Iranians left Baghdad warning that the negotiation process will fail unless there's a change in the terms laid out by the western powers.
The positive meeting in Istanbul, and indications from both sides of a potential confidence-building deal based on halting Iran's enrichment of uranium to 20 per cent purity, left the Iranians shocked by the offer presented in Baghdad: that Iran halt 20 per dent enrichment, ship out its stockpile of such material and cease operations at the Fordow underground plant near Qom. In exchange Iran would be provided with 20 per cent fuel rods for its medical reactor, receive a promise of no further UN sanctions, and be allowed to buy civilian airliner parts.
But on Iran's key demand, for relief from sanctions and the unilateral measures against Iranian oil exports and international trade - negotiators made clear Tehran would get no joy. Iran, meanwhile, says it has already created the 20 per cent fuel it needs, and Russian and Chinese vetoes mean that there will be no meaningful escalation of sanctions via the UN in any case.
Western diplomats told the Iranians that the only way to stop the European oil embargo and measures against Iran's banks from taking effect on July 1 would be to halt all uranium enrichment in line with UN Security Council resolutions. Not only did the Iranians read that as a dramatic retreat by the P5+1, but they stressed that it gave Iran little incentive to make any concessions - so much so that the talks almost collapsed. And within days, Iran appeared to be hardening its stance, with nuclear chief Fereydoon Abbasi insisting that Iran had no intention of halting 20 per cent enrichment, and laying down new conditions for a deal with the International Atomic Energy Agency to inspect suspect sites.
While the parties left Baghdad vowing to reconvene in Moscow on June 18, prospects for sustaining the process appear grim without a significant change on either side of the divide - a change rendered all the more difficult by domestic political realities on both sides.
Mr Obama will struggle to offer any flexibility on the sanctions issue during his election campaign, and without such flexibility, Iran sees little incentive to engage - indeed, without sanctions relief, Ayatollah Khamenei would have a hard time selling any deal to Iran's political system (even in the unlikely event that he'd embrace it).
It may well be that the western powers were simply laying out a maximalist position at the outset of negotiations. But with the Moscow talks scheduled for just two weeks before the most dramatic sanctions yet are to take effect, nuclear diplomacy has turned into a game of brinkmanship in which the political cost of retreat will be high for either side.
The key to the outcome may lie in Moscow, not only as the venue for the next round of talks, but as a key player which, together with China, has opposed the unilateral sanctions being piled on by the western powers. The Obama administration has prioritised unity in the P5+1 precisely because Russian and Chinese involvement have been vital to getting Iran to the table. Should Moscow and Beijing break with their western powers, it will be a lot easier for Iran to withstand and push back against sanctions, particularly those that require the participation of countries outside of the western orbit.
And if Iran is seen to be behaving reasonably, particularly in line with the longstanding Russian proposals for a "step-by-step" approach of reciprocal concessions, the divisions within the P5+1 reported in Baghdad are likely to be exacerbated.
The P5+1 format is, in fact, a double-edged sword. It pressures Iran to deal by aligning its most powerful potential allies with its adversaries, but it also moderates the West's position, and to some extent neutralises the influence of Israel and its hawkish allies in Washington on the position taken by the collective. If the gulf between the sides is to be bridged, Russia- which crafted the framework for renewed talks - will have a key role.
Indeed, if Mr Obama hopes to avoid a crisis and potential confrontation before Americans go to the polls in November, he may be better served by having his diplomats prioritise Russia over Israel. Just as in the Syrian crisis, Washington may be far more dependent on Moscow to help it avoid distasteful choices than it might care to admit.
Tony Karon is a New-York based analyst
On Twitter @TonyKaron