With Iran and the United States engaged in talks over Tehran's nuclear programme since April, Washington's proposal for a deal came after a leaked UN report said Iran had stepped up production of highly enriched uranium.

Iran's top diplomat and lead nuclear negotiator was due to meet the head of the UN's International Atomic Energy Agency (IAEA) in Cairo on Monday, a day after the report was leaked.

Iran has rejected the report, warning it would retaliate if European powers that have threatened to reimpose nuclear sanctions "exploit" the report.

The United States and Western countries have accused Iran of seeking nuclear weapons, a charge Tehran has repeatedly denied, insisting it needs uranium for civilian power production.

Iranian Foreign Minister Abbas Araghchi said on Saturday that he had received "elements" of a US proposal for a nuclear deal following five rounds of talks mediated by Oman.

On Monday, foreign ministry spokesman Esmaeil Baqaei told a news conference in Tehran: "We want to guarantee that the sanctions are effectively lifted...

"So far, the American side has not wanted to clarify this issue," he added.

- 'Red line' -

His remarks come a day after a report by the UN agency showed Iran has stepped up production of uranium enriched up to 60 percent -- close to the roughly 90 percent level needed for atomic weapons.

The US envoy in the nuclear talks said last month that the administration of President Donald Trump would oppose any enrichment.

"An enrichment programme can never exist in the state of Iran ever again. That's our red line. No enrichment," Steve Witkoff told Breitbart News.

Iran has vowed to keep enriching uranium "with or without a deal" on its nuclear programme.

The United States has sent Iran a proposal for a nuclear deal that the White House called "acceptable" and in its "best interest" to accept, US media reported on Saturday.

The New York Times, citing officials familiar with the diplomatic exchanges, said the proposal calls on Iran to stop all enrichment and suggests creating a regional grouping to produce nuclear power.

Iran has held five rounds of talks with the United States in search of a new agreement to replace the deal with major powers that Trump abandoned during his first term in 2018.

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