Rome, Italy - Iranian and US negotiators closed on Friday a fifth round of nuclear talks in Rome with "some but not conclusive progress," mediator Oman said, after a public disagreement over Tehran's uranium enrichment.

The talks, which began in April, are the highest-level contact between the foes since the US quit a landmark 2015 nuclear accord during President Donald Trump's first term.

Since returning to office, Trump has revived his "maximum pressure" campaign on Iran, backing talks but warning of military action if diplomacy fails.

Iran wants a new deal that would ease the sanctions that have battered its economy.

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"The fifth round of Iran US talks have concluded today in Rome with some but not conclusive progress," Omani Foreign Minister Badr Albusaidi said on X, adding that he hoped "the remaining issues" would be clarified in the coming days.

Iranian foreign ministry spokesman Esmaeil Baqaei had earlier said that chief US negotiator Steve Witkoff had left the talks "due to his flight schedule".

The fourth round of talks, in the Omani capital Muscat, ended with a public spat over enrichment.

Witkoff said Washington "could not authorise even one percent" enrichment – a position Tehran called a red line, citing its rights under the nuclear Non-Proliferation Treaty.

Ahead of Friday's talks, Araghchi said "fundamental differences" remained with the US, while adding that Tehran was open to its nuclear sites undergoing more inspections.

"We will not have an agreement at all" if the US wants to prevent Iran from enriching uranium, he said.

The talks came ahead of a June meeting of the UN nuclear watchdog, the Vienna-based International Atomic Energy Agency (IAEA), and the October expiration of the 2015 accord.

The deal, known as the Joint Comprehensive Plan of Action, aimed to allay Western suspicions that Iran was seeking a nuclear weapons capability, an ambition that Tehran has consistently denied.

In return for curbs on its nuclear program, Iran had received relief from international sanctions. But the accord was torpedoed in 2018 when Trump unilaterally withdrew the US and reimposed sanctions.

A year later, Iran responded by ramping up its nuclear activities. It is now enriching uranium to 60% – far above the deal's 3.67% cap but below, though close to, the 90% level needed for a nuclear warhead.