Iran’s Supreme Leader Ayatollah Ali Khamenei on Tuesday voiced scepticism over the outcome of ongoing nuclear talks with the United States, saying negotiations are unlikely to yield a breakthrough amid Washington’s tightening demands.

In remarks published on his official website, Khamenei said, “During (former president Ebrahim) Raisi’s time there were also indirect negotiations that didn’t result in anything, and now we also doubt we will reach a conclusion, and we don’t know what will happen.”

The Supreme Leader strongly criticised the United States’ position on uranium enrichment, calling Washington’s demand that Iran halt enrichment “a big mistake.”

“Tehran will not wait for American permission,” he said. Addressing US negotiators, he added bluntly, “Try not to talk nonsense.”

The comments come as nuclear diplomacy between Tehran and Washington appears to be once again faltering. The two sides held their fourth round of indirect talks earlier this month in Oman, aimed at securing limits on Iran’s nuclear programme in return for sanctions relief. Iranian officials later described the discussions as “difficult.”

The core of the dispute remains Iran’s insistence on its right to enrich uranium — a right it claims under the United Nations’ Nuclear Non-Proliferation Treaty (NPT). The United States, however, has hardened its stance, with special envoy Steve Witkoff stating over the weekend that Washington “cannot allow even 1% of an enrichment capability” under any deal.

“We’ve delivered a proposal to the Iranians that we think addresses some of this without disrespecting them,” Witkoff told ABC News, hinting at possible flexibility but offering no details.

Tehran, however, appeared unimpressed. Deputy Foreign Minister Majid Takht Ravanchi told Iran’s semi-official Nour News on Monday that the talks would “not actually get anywhere” if the US continues to insist on halting enrichment.

Foreign Minister Abbas Araghchi said on Tuesday that while Iran had been offered a date for the next round of talks, “we have yet to accept it.” When asked how negotiations were proceeding, he quipped that both sides were still “tussling.”

The US has sent mixed messages in recent weeks regarding Iran’s enrichment activities. While President Donald Trump, during his visit to the Middle East last week, reiterated threats to use force against Tehran if it does not accept a deal, he stopped short of explicitly denying Iran’s right to enrichment.

With tensions mounting and mutual trust at a low point, prospects for progress appear dim. The location of the next round of talks is expected to be in Europe, but no official confirmation has been made.

Witkoff, despite his stern remarks, struck a hopeful tone, saying, “We hope that it will lead to some real positivity.”