The memorandum of understanding aimed at ending the war between Iran and the US expired on Monday, increasing the risk of a slide back towards open conflict and heightening uncertainty over a diplomatic settlement.
As the deadline edged closer, there was little sign of political will in either Washington or Tehran to extend the 60-day deal or return to the negotiating table.
Instead, the two sides have continued to trade threats, with US President Donald Trump threatening last week to declare the Strait of Hormuz an American territory and Iranian officials signalling readiness to return to war.
Here's what you need to know about the deal and why it failed.
The interim deal was signed on 17 June by Trump and Iran's President Masoud Pezeshkian and came following weeks of high-stakes diplomacy led by Pakistan and Qatar. It kick-started a two-month period during which the two sides committed to the ambitious goal of agreeing to a comprehensive peace agreement settling the intractable dispute over Tehran's nuclear programme.
Kicking the nuclear issue to future negotiations, the MoU was a stop-gap measure that nonetheless sought to address the most immediate crises by imposing a region-wide ceasefire and re-opening the Strait of Hormuz.
Under the deal, both sides agreed to immediately and permanently end military operations across all fronts, including in Lebanon, and to refrain from threats or the use of force.
To resolve the crisis in the strait, the US agreed to lift its blockade on Iranian ports within 30 days in return for Iran lifting restrictions on traffic and demining the area. Tehran said it would waive all fees for 60 days while the final deal was being negotiated. Crucially, it separated the strait's future status from the US-Iran negotiations, empowering Tehran to work with Oman to decide how it would be administered after the war.
Meanwhile, the US agreed to terminate all sanctions on Iran, issue waivers for its oil exports, and unlock some of its frozen assets. It also committed to develop a plan that would see at least $300 billion invested in Iran's reconstruction and economic development.
Iran reiterated its commitment not to seek nuclear weapons and agreed to freeze all nuclear activity while negotiations for a final deal continued.
Iran and the US showed goodwill in the days after the agreement, travelling to Switzerland on 21 June for what was the highest-level meeting between Iranian and American officials in decades. The following day, the US Treasury waived sanctions on Iran's oil exports for two months.
But things began to unravel in the subsequent weeks, with the countries trading accusations of breaching the accord.
On 26 June, Trump accused Iran of a "foolish violation" after a cargo ship was attacked in the Strait. Two days later, Tehran said Washington had broken the agreement following renewed US strikes. At the heart of the disagreement was the strait, which US officials continued to insist should be returned to its pre-war status quo. Iranian officials meanwhile bristled as Trump resumed his incendiary rhetoric, which they said violated the deal.
Officials from both countries soon declared the death of the MoU, and by the middle of July the ceasefire had all but collapsed. For two weeks, the US bombarded southern Iran while Tehran resumed heavy strikes across the Gulf.
Since a fragile peace was restored at the end of the month, there have been few signs that the warring countries are prepared to return to the negotiating table. Instead, both countries have returned to sabre-rattling and contesting control of the strait. Meanwhile, there has been no movement on US sanctions or Iran's frozen assets, while the American military has reimposed its blockade.
"The expiration of the MoU is, in one sense, the formal recognition of a reality that had already emerged," Neil Quilliam, Middle East foreign policy specialist at Chatham House, told The New Arab.
Both countries had already called the deal into question and accused one another of breaking its terms. "In that respect, the end of the MoU confirms the death of a framework that was already struggling to survive," he said.
The wider significance of its expiry lies in what happens next.
"If no alternative framework emerges, both sides will have greater freedom to pursue coercive measures, including military pressure, without the constraints, however weak, imposed by the agreement," Quilliam said. "This increases uncertainty and the risk of miscalculation."
Rather than threatening a military attack, Trump officials have instead signalled a return to economic pressure, with Treasury Secretary Scott Bessent vowing to impose measures that "have never been seen in the history of economic isolation".
The American military's ability to continue defending against Iranian attacks has been called into question in recent weeks following reports of a severe depletion of missile interceptors. It has also been said to have used "virtually all" of its precision long-range missiles.
Iran meanwhile has vowed to resume the war if the US does not agree to its demands. An Iranian official threatened on Monday to go "fully offensive" and escalate in the Gulf in a bid to break the US blockade.
Quilliam said the most likely outcome is a prolonged period of on-off confrontation. Neither side will likely risk a major regional war, but the profound lack of trust will continue to impede meaningful negotiations.
"Barring a major provocation, both Washington and Tehran appear more likely to manage tensions than seek a direct military showdown," he said.
"The danger is that prolonged instability creates repeated opportunities for miscalculation, making the conflict harder to contain over time."