Iran's Supreme Leader, Ali Khamenei, said that nuclear talks with the United States were unlikely to yield any results, amid a diplomatic standoff over the Islamic Republic's enrichment activities.
"We don't think it will lead to any outcome. We don't know what will happen," said Khamenei during a speech on Tuesday, adding that denying Iran's right to enrich uranium was "a big mistake".
Iran and the United States have held four rounds of Omani-mediated nuclear talks since April 12, the highest-level contact between the two foes since Washington abandoned the 2015 nuclear accord.
They had confirmed plans to hold another round of discussions during their last meeting on May 11, which Iran described as "difficult but useful", while a US official said Washington was "encouraged".
Iran currently enriches uranium to 60 percent, far above the 3.67 percent limit set in the 2015 deal and close, though still short of the 90 percent needed for a nuclear warhead.
Western countries, including the United States, have long accused Iran of seeking to acquire atomic weapons, while Iran insists its nuclear programme is for peaceful purposes.
Iran has repeatedly insisted its right to maintain uranium enrichment was "non-negotiable", while chief US negotiator Steve Witkoff has called it a "red line".
On Sunday, Witkoff reiterated that the United States "cannot allow even one percent of an enrichment capability."
"The American side involved in these indirect negotiations should refrain from speaking nonsense," said Khamenei.
Earlier, Iran's Foreign Minister and lead negotiator Abbas Araghchi said, "Enrichment in Iran, however, will continue with or without a deal".
"If the US is interested in ensuring that Iran will not have nuclear weapons, a deal is within reach, and we are ready for a serious conversation to achieve a solution that will forever ensure that outcome," he said in a post on X.
Tensions remain high as Western powers accuse Iran of nearing nuclear weapons capability, which is an allegation Iran firmly denies.
'Maximum pressure'
Iranian diplomats have said Tehran would be open to temporary restrictions on how much uranium it enriches and to what level.
Since returning to the office in January, US President Donald Trump has revived his "maximum pressure" approach against Iran.
While backing nuclear diplomacy, he also warned of potential military action if it fails.
Trump has said he presented Iran's leadership with an "olive branch", adding that it was an offer that would not last forever.
He further threatened to impose "massive maximum pressure", including driving Iranian oil exports to zero if talks failed.
Trump later doubled down on his warning, saying that "something bad is going to happen" unless the Iranians "move quickly" towards a deal.
Iranian officials, however, criticised what they described as "contradictory" positions by US officials along with the continued imposition of sanctions targeting Iran's oil industry and nuclear programme despite the talks.
Araghchi on Tuesday criticised "positions from the United States that were inconsistent with any logic and reason".
Iran's top diplomat said these stances "have caused serious disruptions in the negotiation process."
"As a result, no date has been set for the next round of talks, and the matter remains under review," he added.
On Sunday, Araghchi said Iran has been observing "dissonance ... between what our US interlocutors say in public and in private."
On Friday, Iran held parallel talks with Britain, France and Germany - all parties to the 2015 deal.
They are currently weighing the reimposition of UN sanctions in response to Iranian non-compliance.
The option to trigger the sanctions mechanism expires in October.
Araghchi said Iran was willing to "begin a new chapter" with Europe and urged it to play a role in the nuclear negotiations.
"In its indirect talks with the United States, Iran emphasises its right to peaceful use of nuclear energy and clearly declares that it is not seeking nuclear weapons," Araghchi says.
