TEHRAN: Iran's supreme leader said Monday the Islamic republic could boost uranium enrichment to 60 percent if needed, hours before new limits on inspections by the UN nuclear watchdog went into force.

Ayatollah Ali Khamenei's remarks came ahead of a deadline fixed by Iran's parliament to limit some inspections by the International Atomic Energy Agency (IAEA) unless US sanctions were lifted by Sunday.

Later, Iran's ambassador to the UN agency, Kazem Gharibabadi, said the new limitations would take effect as of midnight (2030 GMT). "The necessary instructions have been issued to the nuclear facilities," he said.

On Sunday, IAEA chief Rafael Grossi held last-ditch talks in Tehran, where the two sides hammered out a temporary technical deal for up to three months that meets the parliament's demands.

The US voiced concern Monday over the temporary arrangement, urging Iran to comply "fully" with verification of its nuclear programme.

The deal comes as Tehran, US President Joe Biden and European powers try to salvage the troubled 2015 nuclear accord, which granted Iran international sanctions relief in return for restrictions on its nuclear programme.

The accord has been nearing collapse since former US president Donald Trump unilaterally withdrew in 2018, reimposing crippling sanctions as part of a "maximum pressure" campaign.

Tehran responded a year later by starting to gradually roll back on key commitments. Early this year it boosted uranium enrichment back to 20 percent, the level it had reached before the nuclear deal.

The Islamic republic has repeatedly denied seeking to build nuclear weapons, a point Khamenei reiterated in comments posted on his official website Monday.

"We will act to the point that is needed and the country requires," he said, adding that "we could bring enrichment to 60 percent" for nuclear propellants and other purposes.

That would far surpass the 3.67 percent limit Iran had accepted under the 2015 deal, but still be short of the 90 percent or so required for an atomic bomb.

"The Islamic republic will not back down on the nuclear issue and will strongly continue down the path of what the country requires for today and tomorrow," Khamenei said.

He stressed that the United States was the party that had left the deal and emphasised that Iran's suspension of its commitments "are still reversible" if Washington returns to its own.