US and Iranian negotiators have scaled back ambitions for a comprehensive peace deal and are instead seeking a temporary memorandum to prevent a return to conflict, two Iranian sources told Reuters.

The shift follows last weekend's inconclusive talks in Islamabad, where deep differences over Iran's nuclear programme — including the fate of its enriched uranium stockpiles and how long Tehran should halt nuclear work — have continued to threaten progress, despite US officials and Pakistani mediators talking up prospects.

A senior Iranian official said the two sides had started to narrow some gaps, including over how to manage the Strait of Hormuz, a vital route for about 20% of the world's oil and gas needs that has been closed to most ships for weeks, according to Reuters.