Iran is poised to reject a US proposal to end a decades-long nuclear dispute, an Iranian diplomat said on Monday, slamming it as a “non-starter” that fails to address Tehran’s interests and leaves Washington’s stance on uranium enrichment unchanged.

“Iran is drafting a negative response to the US proposal, which could be interpreted as a rejection of the US offer,” the senior diplomat, who is close to Iran’s negotiating team, told Reuters.

The US proposal for a new nuclear deal was presented to Iran on Saturday by Oman’s Foreign Minister Sayyid Badr Albusaidi, who was on a short visit to Tehran and has been mediating nuclear talks between Tehran and Washington.

But after five rounds of talks between Iranian Foreign Minister Abbas Araqchi and President Donald Trump’s Middle East envoy Steve Witkoff to resolve the nuclear standoff, many issues remain unresolved.

Among clashing red lines is Iran’s rejection of a US demand that Tehran commit to scrapping uranium enrichment, viewed as a potential pathway to developing nuclear bombs.

Tehran says it wants to master nuclear technology for peaceful purposes and has long denied accusations by Western powers that it is seeking to develop nuclear weapons.

“In this proposal, the US stance on enrichment on Iranian soil remains unchanged, and there is no clear explanation regarding the lifting of sanctions,” said the diplomat, who declined to be identified due to the sensitivity of the matter.

Tehran demands the immediate removal of all US-imposed curbs that impair its oil-based economy. But for the US, the removal of nuclear-related sanctions should be done in phases.

Dozens of Iranian institutions vital to Iran’s economy, including its central bank and national oil company, have been sanctioned since 2018 for, according to Washington, “supporting terrorism or weapons proliferation”.

Trump’s revival of a “maximum pressure” campaign against Tehran since his return to the White House in January has included tightened sanctions and threats to bomb Iran if current negotiations yield no deal.

During his first term, Trump in 2018 ditched Tehran’s 2015 nuclear pact with six powers and reimposed sanctions that have crippled Iran’s economy. In return, Tehran has rapidly violated the 2015 nuclear pact’s curbs on its nuclear programme.

The 2015 deal required Iran to take steps to restrict its nuclear program in return for relief from US, EU and UN economic sanctions.

The diplomat said the assessment of “Iran’s nuclear negotiations committee”, under the supervision of the Supreme Leader Ayatollah Ali Khamenei, was that the US proposal is “completely one-sided” and cannot serve Tehran’s interests.

Therefore, the diplomat said, Tehran considers this proposal a “non-starter” and believes it unilaterally attempts to impose a “bad deal” on Iran through excessive demands.

Two Iranian officials told Reuters last week that Iran may pause uranium enrichment if the US releases frozen Iranian funds and recognises Tehran’s right to refine uranium for civilian use under a “political deal” that could lead to a broader nuclear accord.