Mediators in Islamabad and a United Nations advance team in Muscat worked into the early hours Tuesday to finalize the observation, deconfliction and verification arrangements that will underwrite the Iran-Israel ceasefire, even as both sides traded a final round of strikes hours before the truce is scheduled to take effect at 00:00 GMT on Wednesday.

The diplomatic choreography, sketched out in the Islamabad framework announced Sunday by Pakistani, Saudi and Egyptian mediators, is meant to convert a political agreement into a practical regime of monitors, hotlines and reporting channels in less than 48 hours. Officials involved in the talks said the technical challenge was at least as daunting as the political one, given the geography of the war, the number of belligerents nominally bound by the ceasefire and the absence of any prior verification machinery in the Gulf.

“The political decision was the hard part. The plumbing is almost as hard,” said Karim Al-Habsi, a former Omani diplomat now advising the mediating group as an independent consultant. “You are standing up a monitoring system across two and a half thousand kilometers in roughly 36 hours, with parties that until this morning were still shooting at each other.”

Under the framework, an initial contingent of about 90 U.N. military observers, drawn from troop contributors that include Ireland, India, Bangladesh, Argentina, Ghana and Indonesia, will deploy in three nodes: a maritime cell on Oman’s Musandam Peninsula overlooking the Strait of Hormuz, a southern Yemen cell hosted at Aden to track Houthi compliance, and a small forward team in Baghdad to liaise with the Iraqi government on cross-border launches. A separate Pakistani-led liaison cell will sit in Doha and run a permanent hotline between Iranian and Israeli operations staffs, routed through Qatari mediators rather than directly.

U.N. Secretary-General Antonio Guterres, in a brief statement issued from New York, said the Security Council would be asked to formally endorse the deployment “in the coming days,” but that the advance team had been authorized to begin work immediately under existing standing arrangements. “The window for putting eyes on the ground is narrow, and we intend to use every hour of it,” he said.

Israel’s permanent representative to the U.N., Ambassador Daniel Reuven, told reporters in New York that Israel “welcomes the framework, will respect its terms and will judge it by what happens in the air and at sea, not what is said in capitals.” Iran’s foreign ministry spokesman, Esmaeil Baghaei, said in Tehran that the Islamic Republic was “committed to halting all operations at the agreed moment” and expected reciprocal restraint from Israel, the United States and “armed groups operating in our region,” a reference understood to include both Houthi forces in Yemen and Iraqi militias that have launched rockets across the Iranian border.

That last category has become the diplomats’ most acute worry. In the past 72 hours, a rocket attributed to an Iraqi faction struck near Erbil and a second Houthi launch was intercepted over Saudi airspace, both after the ceasefire framework was unveiled. U.S. Central Command said in a statement Monday evening that there had been “no American casualties” in either incident but that it was tracking the launches as a matter of urgency. American casualties since the war began in early March remain at roughly 350, a figure unchanged for several days.

Layla Hassan, a Beirut-based regional analyst with the Levant Policy Institute, said the proliferation of non-state actors made the next 96 hours uniquely fragile. “A single rogue launch on Wednesday morning could test whether this ceasefire has the political weight to absorb a violation, or whether it cracks on day one,” she said. “The mediators know this. That is why so much of the framework is really about what happens when, not if, somebody fires.”

The framework includes a graduated response mechanism. Reported violations will be triaged within four hours by a joint cell of mediator representatives and U.N. observers; minor incidents are to be handled through quiet de-escalation rather than public condemnation, with formal Security Council referral reserved for systematic breaches. American and Israeli officials pushed back on earlier Iranian proposals for any joint investigative authority that would include Iranian military officers, and that demand was dropped, two officials familiar with the talks said.

In Washington, Secretary of State Marco Rubio held a 40-minute call Monday with Saudi Foreign Minister Faisal bin Farhan and a separate call with Egyptian Foreign Minister Badr Abdelatty, according to a State Department readout. A senior State Department official, speaking on condition of anonymity to describe internal deliberations, said the U.S. position was that “Wednesday is a beginning, not an end,” and that follow-on talks on a longer-term security architecture for the Gulf would begin in earnest only after the first 30 days of compliance.

European capitals were moving in parallel. French Foreign Minister Stéphane Séjourné convened E3 partners in Paris on Monday afternoon to discuss financial and humanitarian support for a post-ceasefire stabilization package, including a possible reactivation of dormant sanctions-relief mechanisms tied to Iranian nuclear transparency. A French diplomatic note circulated to allies and seen by reporters described the European role as “supportive, not central,” and said Paris was prepared to host a follow-on conference in the late spring if the ceasefire stabilizes.

For Pakistan, which has emerged as the surprise convening power of the Islamabad framework, the next 48 hours are also a domestic test. Prime Minister Shehbaz Sharif told a televised audience Monday evening that the country had “carried a message, not a side,” and that Pakistani officers would remain on the ground in Doha and Muscat “for as long as the parties find our presence useful.”

Across the region, the immediate mood was guarded. Markets in Dubai and Tel Aviv held earlier gains; airlines that had suspended Gulf routes signaled they would wait for at least 72 hours of post-ceasefire data before restoring schedules. Diplomats said the most consequential test would come not at midnight Wednesday but on Friday and over the weekend, when the first weekly compliance report from the U.N. advance team is expected to land on the Security Council’s desk.

Mediators said additional technical annexes, including rules for maritime intercepts in the Strait of Hormuz and procedures for handling unidentified launches from Yemeni or Iraqi territory, would be finalized in the hours after the ceasefire takes effect.