***Negotiators who spent months bargaining the 2015 nuclear agreement with Iran say deep mistrust and divergent negotiating styles make rapid new deals unlikely.***[1]

The insight matters because the U.S. and Iran are again exploring a future framework; understanding past challenges helps policymakers gauge realistic timelines and diplomatic hurdles.

Former diplomats and technical advisers said that mutual suspicion was a constant undercurrent. Each side entered talks wary of the other's intentions, often questioning whether concessions would be honored. This mistrust shaped every clause, from uranium enrichment limits to inspection protocols, and still colors current perceptions of any prospective pact.

Cultural and procedural differences also shaped the dialogue. Iranian officials preferred indirect, relationship‑building meetings, while U.S. teams leaned on formal, data‑driven briefings. "Negotiators faced deep mistrust on both sides," one veteran said, highlighting how divergent styles could stall progress even when technical solutions aligned.

The issues themselves were layered. Beyond the headline‑making enrichment caps, the deal involved complex sanctions relief mechanisms, timelines for technology transfer, and verification regimes overseen by the International Atomic Energy Agency. The sheer technical detail required experts to translate scientific jargon into political language, a process that extended negotiations far beyond the public eye.

Even after the JCPOA was signed in 2015, implementation proved uneven, with both parties accusing the other of non‑compliance. The legacy of those disputes informs current skepticism; as one senior adviser said, "A quick new deal is unlikely given the legacy of the 2015 pact," underscoring that past friction still resonates.

**What this means** – The recollections signal that any forthcoming agreement will likely involve protracted confidence‑building measures and a willingness to accommodate divergent negotiating habits. Policymakers should anticipate a multi‑year timeline rather than a swift resolution, and both sides may need to address underlying mistrust before technical details can be finalized.

Negotiators faced deep mistrust on both sides.

The recollections signal that any forthcoming agreement will likely involve protracted confidence‑building measures and a willingness to accommodate divergent negotiating habits. Policymakers should anticipate a multi‑year timeline rather than a swift resolution, and both sides may need to address underlying mistrust before technical details can be finalized.