The US will not accept any level of uranium enrichment by Iran, President Donald Trump’s top negotiator said on Sunday, drawing a “very, very clear red line”.
Envoy for the Middle East Steve Witkoff told ABC News that the US could not permit “even one per cent” of enrichment capability.
“We’ve delivered a proposal to the Iranians that we think addresses some of this without disrespecting them,” Mr Witkoff said.
“We want to get to a solution here. And we think that we will be able to, but everything begins from our standpoint with a deal that does not include enrichment. We cannot have that because enrichment enables weaponisation, and we will not allow a bomb to get there,” he added.
Mr Witkoff emphasised that Mr Trump seeks to resolve the crisis “diplomatically and with dialogue”.
The two sides are expected to meet in Europe “sometime this week”, he said, adding, “We hope that it will lead to some real positivity”.
Iran swiftly dismissed US demands to halt uranium enrichment, calling them "unrealistic" and a barrier to negotiations.
"Unrealistic expectations halt negotiations. Enrichment in Iran cannot be stopped," Foreign Minister Abbas Araqchi said on Sunday, according to the semi-official Tasnim news agency.
Mr Araqchi criticised Mr Witkoff, stating, "He is completely detached from the reality of the negotiations".
The negotiations have reached the “expert” level, meaning the sides are trying to reach agreement on the details of a possible deal. However, a major sticking point remains Iran’s enrichment of uranium, which Tehran insists it must be allowed to do and the Trump administration increasingly insists they must give up.
Mr Trump has repeatedly threatened to unleash air strikes targeting Iran’s programme if a deal is not reached. Iranian officials increasingly warn they could pursue a nuclear weapon with their stockpile of uranium enriched to near weapons-grade levels.

On Gaza humanitarian aid, Mr Witkoff insisted that “there is no daylight” between Mr Trump and Israel’s Prime Minister Benjamin Netanyahu on the issue.
He said that “everyone is concerned about the humanitarian conditions in Gaza” and that Israel indicated that it will begin allowing a lot more of humanitarian aid into Gaza after blocking its entry for more than two and a half months.
“We do not want to see a humanitarian crisis, and we will not allow it to occur on President Trump’s watch,” Mr Witkoff asserted.
The Gaza Humanitarian Foundation, which was established by the US in close co-ordination with Israel to manage aid distribution in a manner that prevents its diversion by Palestinian militant group Hamas, said it would plan to begin operating in Gaza by the end of the month.
The issue now is, said Mr Witkoff, how do we logistically get all of those lorries into Gaza? How do we set up the aid stations?
“There are many … initiatives that we are working on to address this.”
Since early March, Israel has restricted the entry of medical supplies, food, and fuel into Gaza in an effort to pressure Hamas into releasing its hostages. Additionally, Israel has approved plans that could lead to a full-scale takeover of the Gaza Strip, including control over humanitarian aid.
The UN has been warning the international community of an impending famine in the besieged enclave.


